Ethylene Recovery by Absorption

ABSTRACT

A process for recovery of ethylene from a polymerization product stream of a polyethylene production system, comprising separating a light gas stream from the polymerization product stream, wherein the light gas stream comprises ethane and unreacted ethylene, contacting the light gas stream with an absorption solvent system, wherein the contacting the light gas stream with the absorption solvent system occurs at a temperature in a range of from about 40° F. to about 110° F., wherein at least a portion of the unreacted ethylene from the light gas stream is absorbed by the absorption solvent system, and recovering unreacted ethylene from the absorption solvent system to yield recovered ethylene.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 13/446,965 filed Apr. 13, 2012, published as U.S.Patent Application Publication No. US 2012/0232232 A1 and entitled“Ethylene Recovery by Absorption,” which is a continuation-in-part ofU.S. patent application Ser. No. 12/905,966, filed Oct. 15, 2010, nowU.S. Pat. No. 8,410,329 B2, and entitled “Ethylene Separation,” each ofwhich is hereby incorporated herein by reference in its entirety for allpurposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

1. Field of the Invention

This disclosure generally relates to the production of polyethylene.More specifically this disclosure relates to systems and processes forimproving polyethylene production efficiency by decreasing ethylenelosses.

2. Background of the Invention

The production of polymers such as polyethylene from light gasesrequires a high purity feedstock of monomers and comonomers. Due to thesmall differences in boiling points between the light gases in such afeedstock, industrial production of a high purity feedstock may requirethe operation of multiple distillation columns, high pressures, andcryogenic temperatures. As such, the energy costs associated withfeedstock purification represent a significant proportion of the totalcost for the production of such polymers. Further, the infrastructurerequired for producing, maintaining, and recycling high purity feedstockis a significant portion of the associated capital cost.

In order to offset some of the costs and maximize production, it can beuseful to reclaim and/or recycle any unreacted feedstock gases,especially the light hydrocarbon reactants, such as ethylene. Gasescomprising unreacted monomers may be separated from the polymer afterthe polymerization reaction. The polymer is processed while theunreacted monomers are recovered from the gases that are reclaimedfollowing the polymerization reaction. To accomplish this, the reclaimedgas streams have conventionally either been routed through apurification process or redirected through other redundant processingsteps. In either case, conventional processes of recovering monomer havenecessitated energetically unfavorable and expensive processes.

Consequently, there is a need for high-efficiency separation of ethylenefrom a recycle stream.

BRIEF SUMMARY

Disclosed herein is a process for recovery of ethylene from apolymerization product stream of a polyethylene production system,comprising separating a light gas stream from the polymerization productstream, wherein the light gas stream comprises ethane and unreactedethylene, contacting the light gas stream with an absorption solventsystem, wherein the contacting the light gas stream with the absorptionsolvent system occurs at a temperature in a range of from about 40° F.to about 110° F., wherein at least a portion of the unreacted ethylenefrom the light gas stream is absorbed by the absorption solvent system,and recovering unreacted ethylene from the absorption solvent system toyield recovered ethylene.

Further disclosed herein is a polyethylene production process,comprising contacting ethylene and a polymerization catalyst in apolymerization reactor under suitable reaction conditions to yield apolymerization product stream, separating a light gas stream from thepolymerization product stream, wherein the light gas stream comprisesunreacted ethylene, contacting the light gas stream with an absorptionsolvent system in an absorption reactor at a temperature in a range offrom about 40° F. to about 110° F., wherein at least a portion of theunreacted ethylene from the light gas stream is absorbed by theabsorption solvent system to yield a composition comprising a complex ofthe absorption solvent system and unreacted ethylene, removingunabsorbed gases of the light gas stream from contact with theabsorption solvent system, recovering unreacted ethylene from theabsorption solvent system, and contacting the recovered ethylene and thepolymerization catalyst.

Also disclosed herein is a polyethylene production system, comprising afeed stream comprising ethylene, wherein the feed stream ischaracterized by introduction into a polymerization reactor, apolymerization product stream, wherein the polymerization product streamis characterized by emission from the polymerization reactor andintroduction into a separator, a light gas stream comprising unreactedethylene, wherein the light gas stream is characterized by emission fromthe separator, the light gas stream having been separated from thepolymerization product stream, wherein the light gas stream ischaracterized by introduction into an absorption solvent system, whereinthe absorption solvent system has a temperature in a range of from about40° F. to about 110° F., an absorbent-ethylene conjugant, wherein theabsorbent-ethylene conjugant is characterized by formation within theabsorption solvent system by absorption of at least a portion of theunreacted ethylene by the absorption solvent system, and a waste gasstream comprising ethane, wherein the waste gas stream is characterizedby emission from the absorption reactor, wherein the waste gas streamcomprises components of the light gas stream that are not absorbed bythe absorption solvent system, and a recovered unreacted ethylenestream, wherein the recovered unreacted ethylene stream is characterizedby emission from the absorption reactor and reintroduction into thepolymerization reactor.

Also disclosed herein is a polyethylene production system, comprising apolymerization reactor, wherein the polymerization reactor is configuredto receive a feed stream comprising ethylene, and wherein thepolymerization reactor is configured to emit a polymerization productstream, a separator, wherein the separator is configured to receive thepolymerization product stream and to emit a light gas stream comprisingunreacted ethylene, wherein the light gas stream has been separated fromthe polymerization product stream, and an absorption reactor comprisingan absorption solvent system, wherein the absorption reactor isconfigured to receive the light gas stream, to absorb at least a portionof the unreacted ethylene with the absorption solvent system at atemperature in a range of from about 40° F. to about 110° F., and toemit a waste gas stream comprising components of the light gas streamthat are not absorbed by the absorption solvent system, and wherein theabsorption reactor is further configured to emit a recovered unreactedethylene stream, and wherein the polymerization reactor is furtherconfigured to receive the recovered unreacted ethylene stream.

Also disclosed herein is a polyethylene production system, comprising apolymerization reactor, wherein the polymerization reactor is configuredto receive a feed stream comprising ethylene, and wherein thepolymerization reactor is configured to emit a polymerization productstream, a separator, wherein the separator is configured to receive thepolymerization product stream and to emit a light gas stream comprisingunreacted ethylene, wherein the light gas stream has been separated fromthe polymerization product stream, an absorption reactor comprising anabsorption solvent system, wherein the absorption reactor is configuredto receive the light gas stream, to absorb at least a portion of theunreacted ethylene with the absorption solvent system at a temperaturein a range of from about 40° F. to about 110° F. and to emit a waste gasstream comprising components of the light gas stream that are notabsorbed by the absorption solvent system, wherein the absorptionreactor is further configured to emit a complexed stream comprisingethylene absorbed in the absorbent solvent system, and a solventregenerator to regenerate the absorption solvent system, and to emit arecovered unreacted ethylene stream, wherein the polymerization reactoris further configured to receive the recovered unreacted ethylenestream.

The foregoing has outlined rather broadly the features and technicaladvantages of the disclosed inventive subject matter in order that thefollowing detailed description may be better understood. The variouscharacteristics described above, as well as other features, will bereadily apparent to those skilled in the art upon reading the followingdetailed description of the preferred embodiments, and by referring tothe accompanying drawings.

DESCRIPTION OF THE DRAWINGS

For a detailed description of the preferred embodiments of the disclosedprocesses and systems, reference will now be made to the accompanyingdrawings in which:

FIG. 1 illustrates a schematic of a first embodiment of a polyethyleneproduction system;

FIG. 2 illustrates a schematic of a second embodiment of a polyethyleneproduction system;

FIG. 3 illustrates a schematic of a third embodiment of a polyethyleneproduction system;

FIG. 4 illustrates a flow diagram of a first embodiment of apolyethylene production process;

FIG. 5 illustrates a flow diagram of a second embodiment of apolyethylene production process;

FIG. 6 illustrates a flow diagram of a third embodiment of apolyethylene production process;

FIG. 7 is a graph illustrating solubility versus temperature forethylene and ethane in an absorption solvent system;

FIG. 8 illustrates a schematic of an embodiment of an absorption reactorhaving a pressure swing absorption configuration;

FIG. 9 illustrates a schematic of an embodiment of an absorption system;and

FIG. 10 illustrates a schematic of an embodiment of a simulatedabsorption system.

DETAILED DESCRIPTION

Disclosed herein are systems, apparatuses, and processes related to theproduction of polyethylene with improved efficiency. The systems,apparatuses, and processes are generally related to the separation of afirst chemical component or compound from a composition resulting fromthe production of polyethylene and comprising the first chemicalcomponent or compound and one or more other chemical components,compounds, or the like.

Referring to FIG. 1, a first polyethylene production (PEP) system 100 isdisclosed. PEP system 100 generally comprises a purifier 102, reactors104, 106, a separator 108, a processor 110, an absorption reactor 116,and a processing device 114. In the PEP embodiments disclosed herein,various system components may be in fluid communication via one or moreconduits (e.g., pipes, tubing, flow lines, etc.) suitable for theconveyance of a particular stream, for example as show in detail by thenumbered streams in FIGS. 1-3.

In the embodiment of FIG. 1, a feed stream 10 may be communicated to thepurifier 102. A purified feed stream 11 may be communicated from thepurifier 102 to one or more of the reactors 104, 106. Where such asystem comprises two or more reactors, a reactor stream 15 may becommunicated from reactor 104 to reactor 106. A polymerization productstream 12 may be communicated from one or more of the reactors 104, 106to the separator 108. A polymer stream 14 may be communicated from theseparator 108 to the processor 110. A product stream 16 may be emittedfrom the processor 110. A gas stream 18 may be communicated from theseparator 108 to the absorption reactor 116. A waste gas stream 20 maybe communicated from the absorption reactor 116 to the processing device114 and a recycle stream 22 may be communicated from the absorptionreactor 116 to the separator 108. A reintroduction stream 24 may becommunicated from the separator 108 to the purifier 102.

Referring to FIG. 2, a second PEP system 200 is disclosed, which has anumber of system components common with PEP 100. In the alternativeembodiment illustrated by FIG. 2, the second PEP system 200 additionallycomprises a deoxygenator 118. Alternatively to the first PEP system 100(as illustrated in FIG. 1), in the embodiment illustrated by FIG. 2, thegas stream 18 may be communicated to the deoxygenator 118. A treated gasstream 26 may be communicated from the deoxygenator 118 to theabsorption reactor 116.

Referring to FIG. 3, a third PEP system 300 is disclosed, which has anumber of system components common with PEP 100 and PEP 200. In thealternative embodiment illustrated by FIG. 3, the third PEP system 300additionally comprises a regenerator 120 (e.g., a desorption vessel).Alternatively to the first and second PEP systems 100 and 200,respectively, in the embodiment illustrated in FIG. 3, a complexedstream 28 may be communicated from the absorption reactor 116 to theregenerator 120. A recycle stream 22 may be communicated from theregenerator 120 to the separator 108, and a regenerated absorbent stream30 may be communicated from the regenerator 120 to the absorptionreactor 116.

In FIG. 3, a temperature of lean solvent may be taken from stream 30.The temperature of the absorption reactor 116 may depend on atemperature of gas stream 18, a temperature of lean solvent in stream30, a heat of solution, and a heat of reaction. In the disclosedembodiments, the mass flow rate of lean solvent in stream 30 may be 50to 300 times greater than a mass flow rate of the gas stream 18.Therefore, the temperature of the absorption reactor 116 may highlydepend on the temperature of lean solvent in the disclosed embodiments.

Various embodiments of suitable PEP systems having been disclosed,embodiments of a PEP process are now disclosed. One or more of theembodiments of a PEP process may be described with reference to one ormore of PEP system 100, PEP system 200, and/or PEP system 300. Althougha given PEP process may be described with reference to one or moreembodiments of a PEP system, such a disclosure should not be construedas so-limiting. Although the various steps of the processes disclosedherein may be disclosed or illustrated in a particular order, suchshould not be construed as limiting the performance of these processesto any particular order unless otherwise indicated.

Referring to FIG. 4, a first PEP process 400 is illustrated. PEP process400 generally comprises at block 51 purifying a feed stream, at block 52polymerizing monomers of the purified feed stream to form apolymerization product, at block 53 separating the polymerizationproduct into a polymer stream and a gas stream, at block 54 processingthe polymer stream, at block 55 separating at least one gaseouscomponent from the gas stream to form a recycle stream and a wastestream, and at block 56 combusting the waste stream.

In an embodiment, the first PEP process 400 or a portion thereof may beimplemented via the first PEP system 100 (e.g., as illustrated in FIG.1). Referring to FIGS. 1 and 4, in an embodiment the feed stream 10 maycomprise a gaseous reactant, particularly, ethylene. In an embodiment,purifying the feed stream may yield a purified stream 11 comprisingsubstantially pure monomers (e.g., ethylene monomers), comonomers (e.g.,butene-1 comonomers, or combinations thereof. Polymerizing monomers(optionally, comonomers) of the purified stream 11 may yield thepolymerization product stream 12 generally comprising unreacted monomer(e.g., ethylene), optional unreacted comonomer (e.g., butene-1),by-products (e.g., ethane, which may be by-product ethane formed fromethylene and hydrogen), and a polymerization product (e.g., polymer andoptionally, copolymer). Separating the polymerization product stream 12may yield the polymer stream 14 (e.g., polyethylene polymer, copolymer)and the gas stream 18 generally comprising unreacted monomer (e.g.,ethylene monomer and any optional comonomer such as butene-1) andvarious waste gases (e.g., ethane). Processing the polymer stream 14 mayyield the product stream 16. Separating at least one gaseous componentfrom the gas stream 18 may yield a recycle stream 22, generallycomprising unreacted ethylene monomer (optionally, unreacted comonomer),and a waste gas stream 20. In an embodiment, separating the gas stream18 comprises absorbing ethylene from the gas stream 18 to yield thewaste gas stream 20 and then releasing the absorbed ethylene to form therecycle stream 22. The recycle stream 22, comprising ethylene, may bepressurized (e.g., returned to the separator 108 for pressurization) andre-introduced into a PEP process (e.g., PEP process 400) asreintroduction stream 24. Combusting the waste gas stream 20 may becarried out with a flare as the processing device 114.

Referring to FIG. 5, a second PEP process 500 is illustrated, which hasa number of process steps common with PEP process 400. In thealternative embodiment illustrated by FIG. 5, block 55 of FIG. 4 isenhanced by at block 57 treating the gas stream to form a treated gasstream and at block 55′ separating at least one gaseous component fromthe treated gas stream to form a recycle stream and a waste stream.

In an embodiment, second PEP process 500 or a portion thereof may beimplemented via the second PEP system 200 (e.g. as illustrated in FIG.2). Alternatively to the embodiments of FIGS. 1 and 4, in the embodimentof FIGS. 2 and 5 treating the gas stream 18 may yield the treated gasstream 26. In an embodiment, treating the gas stream 18 comprisesdeoxygenating the gas stream 18. Separating at least one gaseouscomponent from the treated gas stream 26 may yield a recycle stream 22,generally comprising unreacted ethylene monomer (optionally, comonomer),and a waste gas stream 20.

Referring to FIG. 6, a third PEP process 600 is illustrated, which has anumber of process steps common with PEP process 500. In the alternativeembodiment illustrated by FIG. 6, block 55′ of FIG. 5 is enhanced by atblock 55″ separating at least one gaseous component from the treated gasstream to form a complexed stream and a waste gas stream and at block 58separating the complexed stream into an absorbent stream and a recyclestream.

In an embodiment, third PEP process 600 or a portion thereof may beimplemented via the third PEP system 300 (e.g. as illustrated in FIG.3). Alternatively to the embodiments of FIGS. 1 & 4 and 2 & 5, in theembodiment of FIGS. 3 and 6 separating at least one gaseous componentfrom the treated gas stream 26 may yield an unreacted monomer-absorbent(e.g., an ethylene-absorbent) in complexed stream 28. In an embodiment,separating the unreacted monomer-absorbent complexed stream 28 comprisesreleasing the absorbed ethylene to form a recycle stream 22 and aregenerated absorbent stream 30. In the embodiment of FIGS. 3 and 6,separating at least one gaseous component from the treated gas stream 26may yield an unreacted comonomer-absorbent (e.g., a butene-1-absorbent)in complexed stream 28. In an embodiment, separating the unreactedcomonomer-absorbent in complexed stream 28 comprises releasing theabsorbed comonomer to form a recycle stream 22 and a regeneratedabsorbent stream 30.

In one or more of the embodiments disclosed herein, purifying a feedstream (e.g., at block 51) may comprise separating unwanted compoundsand elements from a feed stream comprising ethylene to form a purifiedfeed stream. In an embodiment, the feed stream may comprise ethylene andvarious other gases, such as but not limited to methane, ethane,acetylene, propylene, various other hydrocarbons having three or morecarbon atoms, or combinations thereof. In an embodiment, purifying afeed stream may comprise any suitable method or process, including thenon-limiting examples filtering, membrane screening, reacting withvarious chemicals, absorbing, adsorbing, distillation(s), orcombinations thereof.

In embodiments as illustrated by FIGS. 1-3, purifying a feed stream maycomprise routing the feed stream 10 to the purifier 102. In one or moreof the embodiments disclosed herein, the purifier 102 may comprise adevice or apparatus suitable for the purification of one or morereactant gases in a feed stream comprising a plurality of potentiallyunwanted gaseous compounds, elements, contaminants, or the like.Non-limiting examples of a suitable purifier 102 may comprise a filter,a membrane, a reactor, an absorbent, a molecular sieve, one or moredistillation columns, or combinations thereof. The purifier 102 may beconfigured to separate ethylene from a stream comprising methane,ethane, acetylene, propane, propylene, water, oxygen various othergaseous hydrocarbons, various contaminants, and/or combinations thereof.

In an embodiment, purifying a feed stream may yield a purified feed 11comprising substantially pure ethylene. In an embodiment, the purifiedfeed stream may comprise less than 25% by total weight of the stream,alternatively, less than about 10%, alternatively, less than about 1.0%of any one or more of nitrogen, oxygen, methane, ethane, propane, orcombinations thereof. As used herein “substantially pure ethylene”refers to a fluid stream comprising at least about 60% ethylene,alternatively, at least about 70% ethylene, alternatively, at leastabout 80% ethylene, alternatively, at least about 90% ethylene,alternatively, at least about 95% ethylene, alternatively, at leastabout 99% ethylene by total weight of the stream, alternatively, atleast about 99.5% ethylene by total weight of the stream. In anembodiment, the feed stream 11 may further comprise trace amounts ofethane, for example, as from a recycle stream as will be discussed.

In one or more of the embodiments disclosed herein, polymerizingmonomers of the purified feed (e.g., at block 52) may comprise allowinga polymerization reaction between a plurality of monomers by contactinga monomer or monomers with a catalyst system under conditions suitablefor the formation of a polymer. In one or more of the embodimentsdisclosed herein, polymerizing comonomers (e.g., at block 52) maycomprise allowing a polymerization reaction between a plurality ofcomonomers by contacting a comonomer or comonomers with a catalystsystem under conditions suitable for the formation of a copolymer. In anembodiment, any suitable catalyst system may be employed. A suitablecatalyst system may comprise a catalyst and, optionally, a co-catalystand/or promoter. Nonlimiting examples of suitable catalyst systemsinclude Ziegler Natta catalysts, Ziegler catalysts, chromium catalysts,chromium oxide catalysts, chromocene catalysts, metallocene catalysts,nickel catalysts, or combinations thereof. Catalyst systems suitable foruse in this disclosure have been described, for example, in U.S. Pat.No. 7,619,047 and U.S. Patent Application Publication Nos. 2007/0197374,2009/0004417, 2010/0029872, 2006/0094590, and 2010/0041842, each ofwhich is incorporated by reference herein in its entirety.

In embodiments as illustrated by FIGS. 1-3, polymerizing monomers of thepurified feed may comprise routing the feed stream 11 to thepolymerization reactors or “reactors” 104, 106. In one or more of theembodiments disclosed herein, the reactors 104, 106 may comprise anyvessel or combination of vessels suitably configured to provide anenvironment for a chemical reaction (e.g., a contact zone) betweenmonomers (e.g., ethylene) and/or polymers (e.g., an “active” or growingpolymer chain), and optionally comonomers (e.g., butene-1) and/orcopolymers, in the presence of a catalyst to yield a polymer (e.g., apolyethylene polymer) and/or copolymer. Although the embodimentsillustrated in FIGS. 1, 2, and 3, illustrate various PEP systems havingtwo reactors in series, one of skill in the art viewing this disclosurewill recognize that one reactor, alternatively, any suitable numberand/or configuration of reactors may be employed.

As used herein, the terms “polymerization reactor” or “reactor” includeany polymerization reactor capable of polymerizing olefin monomers orcomonomers to produce homopolymers or copolymers. Such homopolymers andcopolymers are referred to as resins or polymers. The various types ofreactors include those that may be referred to as batch, slurry,gas-phase, solution, high pressure, tubular or autoclave reactors. Gasphase reactors may comprise fluidized bed reactors or staged horizontalreactors. Slurry reactors may comprise vertical or horizontal loops.High pressure reactors may comprise autoclave or tubular reactors.Reactor types can include batch or continuous processes. Continuousprocesses could use intermittent or continuous product discharge.Processes may also include partial or full direct recycle of unreactedmonomer, unreacted comonomer, and/or diluent.

Polymerization reactor systems of the present disclosure may compriseone type of reactor in a system or multiple reactors of the same ordifferent type. Production of polymers in multiple reactors may includeseveral stages in at least two separate polymerization reactorsinterconnected by a transfer device making it possible to transfer thepolymers resulting from the first polymerization reactor (e.g., reactor104) into the second reactor (e.g., reactor 106). The desiredpolymerization conditions in one of the reactors may be different fromthe operating conditions of the other reactors. Alternatively,polymerization in multiple reactors may include the manual transfer ofpolymer from one reactor to subsequent reactors for continuedpolymerization. Multiple reactor systems may include any combinationincluding, but not limited to, multiple loop reactors, multiple gasreactors, a combination of loop and gas reactors, multiple high pressurereactors or a combination of high pressure with loop and/or gasreactors. The multiple reactors may be operated in series or inparallel.

According to one aspect, the polymerization reactor system may compriseat least one loop slurry reactor comprising vertical or horizontalloops. Monomer, diluent, catalyst, and optionally any comonomer, may becontinuously fed to a loop reactor where polymerization occurs.Generally, continuous processes may comprise the continuous introductionof a monomer, an optional comonomer, a catalyst, and a diluent into apolymerization reactor and the continuous removal from this reactor of asuspension comprising polymer particles and the diluent. Reactoreffluent may be flashed to remove the solid polymer from the liquidsthat comprise the diluent, monomer and/or comonomer. Varioustechnologies may be used for this separation step including but notlimited to, flashing that may include any combination of heat additionand pressure reduction; separation by cyclonic action in either acyclone or hydrocyclone; or separation by centrifugation.

In one or more embodiments, a comonomer may comprise unsaturatedhydrocarbons having 3 to 12 carbon atoms. For example, a comonomer maycomprise propene, butene-1, hexene-1, octenes, or combinations thereof.

A typical slurry polymerization process (also known as the particle formprocess), is disclosed, for example, in U.S. Pat. Nos. 3,248,179,4,501,885, 5,565,175, 5,575,979, 6,239,235, 6,262,191 and 6,833,415,each of which is incorporated by reference in its entirety herein.

In embodiments, suitable diluents used in slurry polymerization include,but are not limited to, the monomer, and optionally, the comonomer,being polymerized and hydrocarbons that are liquids under reactionconditions. Examples of suitable monomer diluents include, but are notlimited to, hydrocarbons such as propane, cyclohexane, isobutane,n-butane, n-pentane, isopentane, neopentane, and n-hexane. Inembodiments, comonomer diluents may comprise unsaturated hydrocarbonshaving 3 to 12 carbon atoms. Examples of suitable comonomer diluentsinclude, but are not limited to propene, butene-1, hexene-1, octenes, orcombinations thereof. Some loop polymerization reactions can occur underbulk conditions where no diluent is used. An example is polymerizationof propylene monomer as disclosed in U.S. Pat. Nos. 5,455,314, which isincorporated by reference herein in its entirety.

According to yet another aspect, the polymerization reactor may compriseat least one gas phase reactor. Such systems may employ a continuousrecycle stream containing one or more monomers continuously cycledthrough a fluidized bed in the presence of the catalyst underpolymerization conditions. A recycle stream may be withdrawn from thefluidized bed and recycled back into the reactor. Simultaneously,polymer product may be withdrawn from the reactor and new or freshmonomer may be added to replace the polymerized monomer Likewise,copolymer product may optionally be withdrawn from the reactor and newor fresh comonomer may be added to replace polymerized comonomer,polymerized monomer, or combinations thereof. Such gas phase reactorsmay comprise a process for multi-step gas-phase polymerization ofolefins, in which olefins are polymerized in the gaseous phase in atleast two independent gas-phase polymerization zones while feeding acatalyst-containing polymer formed in a first polymerization zone to asecond polymerization zone. One type of gas phase reactor is disclosedin U.S. Pat. Nos. 5,352,749, 4588,790 and 5,436,304, each of which isincorporated by reference in its entirety herein.

According to still another aspect, a high pressure polymerizationreactor may comprise a tubular reactor or an autoclave reactor. Tubularreactors may have several zones where fresh monomer (optionally,comonomer), initiators, or catalysts may be added. Monomer (optionally,comonomer) may be entrained in an inert gaseous stream and introduced atone zone of the reactor. Initiators, catalysts, and/or catalystcomponents may be entrained in a gaseous stream and introduced atanother zone of the reactor. The gas streams may be intermixed forpolymerization. Heat and pressure may be employed appropriately toobtain optimal polymerization reaction conditions.

According to yet another aspect, the polymerization reactor may comprisea solution polymerization reactor wherein the monomer (optionally,comonomer) may be contacted with the catalyst composition by suitablestirring or other means. A carrier comprising an inert organic diluentor excess monomer (optionally, comonomer) may be employed. If desired,the monomer and/or optional comonomer may be brought in the vapor phaseinto contact with the catalytic reaction product, in the presence orabsence of liquid material. The polymerization zone is maintained attemperatures and pressures that will result in the formation of asolution of the polymer in a reaction medium. Agitation may be employedto obtain better temperature control and to maintain uniformpolymerization mixtures throughout the polymerization zone. Adequatemeans are utilized for dissipating the exothermic heat ofpolymerization.

Polymerization reactors suitable for the disclosed systems and processesmay further comprise any combination of at least one raw material feedsystem, at least one feed system for catalyst or catalyst components,and/or at least one polymer recovery system. Suitable reactor systemsmay further comprise systems for feedstock purification, catalyststorage and preparation, extrusion, reactor cooling, polymer recovery,fractionation, recycle, storage, loadout, laboratory analysis, andprocess control.

Conditions that are controlled for polymerization efficiency and toprovide resin properties include temperature, pressure and theconcentrations of various reactants. Polymerization temperature canaffect catalyst productivity, polymer molecular weight and molecularweight distribution. Suitable polymerization temperature may be anytemperature below the de-polymerization temperature according to theGibbs Free energy equation. Typically this includes from about 60° C. toabout 280° C., for example, and from about 70° C. to about 110° C.,depending upon the type of polymerization reactor.

Suitable pressures will also vary according to the reactor andpolymerization type. The pressure for liquid phase polymerizations in aloop reactor is typically less than 1000 psig. Pressure for gas phasepolymerization is usually at about 200 to 500 psig. High pressurepolymerization in tubular or autoclave reactors is generally run atabout 20,000 to 75,000 psig. Polymerization reactors can also beoperated in a supercritical region occurring at generally highertemperatures and pressures. Operation above the critical point of apressure/temperature diagram (supercritical phase) may offer advantages.In an embodiment, polymerization may occur in an environment having asuitable combination of temperature and pressure. For example,polymerization may occur at a pressure in a range from about 550 psi toabout 650 psi, alternatively, about 600 psi to about 625 psi and atemperature in a range from about 170° F. to about 230° F.,alternatively, from about 195° F. to about 220° F.

The concentration of various reactants can be controlled to produceresins with certain physical and mechanical properties. The proposedend-use product that will be formed by the resin and the method offorming that product determines the desired resin properties. Mechanicalproperties include tensile, flexural, impact, creep, stress relaxationand hardness tests. Physical properties include density, molecularweight, molecular weight distribution, melting temperature, glasstransition temperature, temperature melt of crystallization, density,stereoregularity, crack growth, long chain branching and rheologicalmeasurements.

The concentrations and/or partial pressures of monomer, comonomer,hydrogen, co-catalyst, modifiers, and electron donors are important inproducing these resin properties. Comonomer may be used to controlproduct density. Hydrogen may be used to control product molecularweight. Cocatalysts can be used to alkylate, scavenge poisons andcontrol molecular weight. Modifiers can be used to control productproperties and electron donors affect stereoregularity, the molecularweight distribution, or molecular weight. In addition, the concentrationof poisons is minimized because poisons impact the reactions and productproperties.

In an embodiment, polymerizing monomers of the purified feed maycomprise introducing a suitable catalyst system into the first and/orsecond reactor 104, 106, respectively, so as to form a slurry.Alternatively, a suitable catalyst system may reside in the first and/orsecond reactor 104, 106, respectively.

As explained above, polymerizing monomers of the purified feed maycomprise selectively manipulating one or more polymerization reactionconditions to yield a given polymer product, to yield a polymer producthaving one or more desirable properties, to achieve a desiredefficiency, to achieve a desired yield, the like, or combinationsthereof. Non-limiting examples of such parameters include temperature,pressure, type and/or quantity of catalyst or co-catalyst, and theconcentrations and/or partial pressures of various reactants. In anembodiment, polymerizing monomers of the purified feed 52 may compriseadjusting one or more polymerization reaction conditions.

In an embodiment, polymerizing monomers of the purified feed maycomprise maintaining a suitable temperature, pressure, and/or partialpressure(s) during the polymerization reaction, alternatively, cyclingbetween a series of suitable temperatures, pressures, and/or partialspressure(s) during the polymerization reaction.

In an embodiment, polymerizing monomers of the purified feed maycomprise circulating, flowing, cycling, mixing, agitating, orcombinations thereof, the monomers (optionally, comonomers), catalystsystem, and/or the slurry within and/or between the reactors 104, 106.In an embodiment where the monomers (optionally, comonomers), catalystsystem, and/or slurry are circulated, circulation may be at a velocity(e.g., slurry velocity) of from about 1 m/s to about 30 m/s,alternatively, from about 2 m/s to about 17 m/s, alternatively, fromabout 3 m/s to about 15 m/s.

In an embodiment, polymerizing monomers of the purified feed maycomprise configuring reactors 104, 106 to yield a multimodal (e.g., abimodal) polymer (e.g., polyethylene). For example, the resultantpolymer may comprise both a relatively high molecular weight, lowdensity (HMWLD) polyethylene polymer and a relatively low molecularweight, high density (LMWHD) polyethylene polymer. For example, varioustypes of suitable polymers may be characterized as having a variousdensities. For example, a Type I may be characterized as having adensity in a range of from about 0.910 g/cm³ to about 0.925 g/cm³,alternatively, a Type II may be characterized as having a density fromabout 0.926 g/cm³ to about 0.940 g/cm³, alternatively, a

Type III may be characterized as having a density from about 0.941 g/cm³to about 0.959 g/cm³, alternatively, a Type IV may be characterized ashaving a density of greater than about 0.960 g/cm³.

In an embodiment, polymerizing monomers may comprise polymerizingcomonomers in one or more of polymerization reactors 104, 106.

In the embodiments illustrated in FIGS. 1-3, polymerizing monomers ofthe purified feed may yield a polymerization product stream 12. Such apolymerization product stream 12 may generally comprise various solids,semi-solids, volatile and nonvolatile liquids, gases and combinationsthereof. In an embodiment, the polymerization product stream 12 maycomprise hydrogen, nitrogen, methane, ethylene, ethane, propylene,propane, butane, isobutane, pentane, hexane, hexene-1 and heavierhydrocarbons. In an embodiment, ethylene may be present in a range offrom about 0.1% to about 15%, alternatively, from about 1.5% to about5%, alternatively, about 2% to about 4% by total weight of the stream.Ethane may be present in a range of from about 0.001% to about 4%,alternatively, from about 0.2% to about 0.5% by total weight of thestream. Isobutane may be present in a range from about 80% to about 98%,alternatively, from about 92% to about 96%, alternatively, about 95% bytotal weight of the stream.

The solids and/or liquids may comprise a polymer product (e.g., apolyethylene polymer), often referred to at this stage of the PEPprocess as “polymer fluff.” The gases may comprise unreacted, gaseousreactant monomers or optional comonomers (e.g., unreacted ethylenemonomers, unreacted butene-1 monomers), gaseous waste products, gaseouscontaminants, or combinations thereof.

In one or more of the embodiments disclosed herein, separating thepolymerization product into a polymer stream and a gas stream (e.g., atblock 53) may generally comprise removing any gases from liquids and/orsolids (e.g., the polymer fluff) by any suitable process.

In embodiments as illustrated by FIGS. 1-3, separating thepolymerization product into a polymer stream and a gas stream maycomprise routing the polymerization product steam 12 to the separator108. In one or more of the embodiments disclosed herein, the separator108 may be configured to separate a stream (e.g., polymerization productcomprising polyethylene) into gases, liquids, solids, or combinationsthereof. The reaction product may comprise unreacted, gaseous monomersor optional comonomers (e.g., unreacted ethylene monomers, unreactedbutene-1 monomers), gaseous waste products, and/or gaseous contaminants.As used herein, an “unreacted monomer,” for example, ethylene, refers toa monomer that was introduced into a polymerization reactor during apolymerization reaction but was not incorporated into a polymer. As usedherein, an “unreacted comonomer,” for example, butene-1, refers to acomonomer that was introduced into a polymerization reactor during apolymerization reaction but was not incorporated into a polymer.

In an embodiment, the separator 108 may comprise a vapor-liquidseparator. Suitable examples of such a separator may include adistillation column, a flash tank, a filter, a membrane, a reactor, anabsorbent, an adsorbent, a molecular sieve, or combinations thereof. Inan embodiment, the separator comprises a flash tank. Not seeking to bebound by theory, such a flash tank may comprise a vessel configured tovaporize and/or remove low vapor pressure components from a hightemperature and/or high pressure fluid. The separator 108 may beconfigured such that an incoming stream may be separated into a liquidstream (e.g., a condensate stream) and a gas (e.g., vapor) stream. Theliquid or condensate stream may comprise a reaction product (e.g.,polyethylene, often referred to as “polymer fluff”). The gas or vaporstream may comprise volatile solvents, gaseous, unreacted monomersand/or optional comonomers, waste gases (secondary reaction products,such as contaminants and the like), or combinations thereof. Theseparator may be configured such that the feed stream is flashed byheat, pressure reduction, or both such that the enthalpy of the streamis increased. This may be accomplished via a heater, a flashline heater,various other operations commonly known in the art, or combinationsthereof. For example, a flash line heater comprising a double pipe mayexchange heat by hot water or steam. Such a flashline heater mayincrease the temperature of the stream while reducing its pressure.

In an embodiment, separating the polymerization product into a polymerstream and a gas stream may comprise distilling, vaporizing, flashing,filtering, membrane screening, absorbing, adsorbing, or combinationsthereof, the polymerization product. In the embodiments illustrated inFIGS. 1-3, separating the polymerization product into a polymer streamand a gas stream yields a gas stream 18 and a polymer stream 14. In anembodiment, the gas stream 18 may comprise hydrogen, nitrogen, methane,ethylene, ethane, propylene, propane, butane, isobutane, pentane,hexane, hexene-1 and heavier hydrocarbons. In an embodiment, ethylenemay be present in a range of from about 0.1% to about 15%,alternatively, from about 1.5% to about 5%, alternatively, about 2% toabout 4% by total weight of the stream. Ethane may be present in a rangeof from about 0.001% to about 4%, alternatively, from about 0.2% toabout 0.5% by total weight of the stream. Isobutane may be present in arange from about 80% to about 98%, alternatively, from about 92% toabout 96%, alternatively, about 95% by total weight of the stream.

In one or more one or more of the embodiments disclosed herein,processing the polymer stream (e.g., at block 54) comprises any suitableprocess or series of processes configured to produce a polymer productas may be suitable for commercial or industrial usage, storage,transportation, further processing, or combinations thereof.

In embodiments as illustrated by FIGS. 1-3, processing the polymerstream may comprise routing the polymer stream 14 to the processor 110.The processor 110 may be configured for the performance of a suitableprocessing means, nonlimiting examples of which include cooling,injection molding, melting, pelletizing, blow molding, extrusionmolding, rotational molding, thermoforming, cast molding, the like, orcombinations thereof. Various additives and modifiers may be added tothe polymer to provide better processing during manufacturing and fordesired properties in the end product. Nonlimiting examples of suchadditives may include surface modifiers such as slip agents, antiblocks,tackifiers; antioxidants such as primary and secondary antioxidants;pigments; processing aids such as waxes/oils and fluoroelastomers; andspecial additives such as fire retardants, antistats, scavengers,absorbers, odor enhancers, and degradation agents.

In an embodiment, the processor 110 may be configured to form a suitablepolymer product. Nonlimiting examples of suitable polymer products asmay result from such processing include films, powders, pellets, resins,liquids, or any other suitable form as will be appreciated by those ofskill in the art. Such a suitable output may be for use in, forexamples, one or more of various consumer or industrial products. Forexample, the polymer product may be utilized any one or more of variousarticles, including, but not limited to, bottles, drums, toys, householdcontainers, utensils, film products, drums, fuel tanks, pipes,geomembranes, and liners. In a particular embodiment, the processor isconfigured to form pellets for transportation to a consumer productmanufacturer. For example, in the embodiments illustrated in FIGS. 1-3,processing the polymer stream yields a polymer product 16 (e.g.,pelletized polyethylene).

In one or more one or more of the embodiments disclosed herein, treatingthe gas stream (e.g., at block 57) comprises any suitable process orreaction for removing oxygen, oxygenated compounds, oxidizing compounds,or combinations thereof (cumulatively referred to herein as “oxygen”)from the gas stream. Suitable processes or reactions will be appreciatedby those of skill in the art viewing this disclosure. Nonlimitingexamples of suitable processes for removing oxygen include variouscatalyzed reactions, contacting with a chemical species known to reactwith oxygen, filtering, absorbing, adsorbing, heating, cooling, orcombinations thereof.

In embodiments as illustrated by FIGS. 2-3, treating the gas stream maycomprise routing the gas stream 18 to the deoxygenator 118. In one ormore one or more of the embodiments disclosed herein, the deoxygenator118 may comprise a device or apparatus configured for the removaloxygen, from a gas stream. Nonlimiting examples of a suitabledeoxygenator include various reactors (e.g., a fluidized bed reactor ora fixed bed), a filter, or combinations thereof. A suitable deoxygenator118 may be configured to reduce, prevent, or exclude compounds and/orelements (e.g., oxygen) that may have the effect of poisoning anabsorption solvent from reaching the absorption reactor (e.g., as willbe disclosed herein).

In the embodiments illustrated by FIGS. 2-3, treating the gas streamyields a treated gas stream 26 being substantially free of oxygen. Asused herein “substantially free of oxygen” refers to a fluid streamcomprising no more than least about 5% oxygen, alternatively, no morethan about 1% oxygen, alternatively, no more than about 0.1% oxygen,alternatively, no more than about 0.01% oxygen by total weight of thestream.

In one or more one or more of the embodiments disclosed herein,separating at least one gaseous component from the gas stream and/or thetreated gas stream, collectively referred to as a gas stream, (e.g., atblock 55, 55′, or 55″) generally comprises any suitable method ofselectively separating at least a first chemical component or compoundfrom a stream comprising the first chemical component or compound andone or more other chemical components, compounds, or the like. Invarious embodiments, the gaseous component separated from the gas streammay comprise one or more hydrocarbons. Nonlimiting examples of suchhydrocarbons include alkanes (e.g., butane, particularly, isobutane) andalkenes or olefin monomers (e.g., ethylene) or optional comonomers(e.g., butene-1). In an embodiment, the gaseous component separated fromthe gas stream may comprise an unreacted hydrocarbon monomer, e.g.,ethylene. Optionally, the gaseous component separated from the gasstream may comprise an unreacted hydrocarbon comonomer, e.g., propene.In an embodiment, the gaseous component separated from the gas streammay comprise an unreacted hydrocarbon monomer (e.g., ethylene, alone orin combination with other hydrocarbons, such as, isobutane), oroptionally, hydrocarbon comonomer (e.g., propene, alone or incombination with other hydrocarbons, such as, isobutane). In anembodiment, the gaseous component separated from the gas stream maycomprise ethylene, alone or in combination with isobutane. In anembodiment, capturing isobutane may result in a savings of the cost ofthe captured isobutane and reduce the presence of isobutane in flareemissions. Nonlimiting examples of suitable separating means includedistilling, vaporizing, flashing, filtering, membrane screening,absorbing, adsorbing, molecular weight exclusion, size exclusion,polarity-based separation, or combinations thereof.

In an embodiment, separating at least one gaseous component from the gasstream may comprise contacting the gas stream with the absorbent (e.g.,an absorption solvent system, as will be disclosed herein), for example,so as to allow the gaseous component to be absorbent by the absorbent.In such an embodiment, separating at least one gaseous component fromthe gas stream comprises selectively absorbing the at least one gaseouscomponent from a gas stream. In such an embodiment, absorbing the atleast one gaseous component from the gas stream generally comprisescontacting the gas stream with a suitable absorbent, allowing the atleast one component to be absorbed by the absorbent, and, optionally,removing a waste stream comprising unabsorbed gases. In an additionalembodiment, separating at least one gaseous component from the gasstream may further comprise liberating the absorbed gaseous componentfrom the absorbent.

In an embodiment, contacting the gas stream with the absorbent maycomprise any suitable means of ensuring sufficient contact between thegas stream and the absorbent. Nonlimiting examples of suitable means bywhich to provide sufficient contact between the gas stream and theabsorbent include the use of various reactor systems, such as thosedisclosed above (e.g., an absorption column or sparged or mixed tank).Not intending to limited by theory, a suitable reactor system may ensurecontact between a two or more gaseous, liquid, and or solid compositionsby agitating or mixing the two components in the presence of each other,circulating, dispersing, or diffusing a first composition through orwithin a second composition, or various other techniques known to thoseof skill in the art. In an embodiment, the gas stream and the absorbentmay be brought into contact in a suitable ratio. Such a suitable ratioof gas stream to absorbent may be in a range of from about 1,000lb/hr:1000 gpm to about 2,500 lb/hr:25 gpm, alternatively, from about1000 lb/hr:250 gpm to about 2500 lb/hr:100 gpm, alternatively, about1875 lb/hr:250 gpm.

In an embodiment as illustrated by FIGS. 1-3, separating at least onegaseous component from the gas stream (e.g., gas stream 18 of FIG. 1 ortreated gas stream 26 of FIGS. 2-3) may comprise routing the gas streamto the absorption reactor 116. In one or more of the embodimentsdisclosed herein, the absorption reactor 116 may comprise a reactorconfigured to selectively absorb at least a first chemical component orcompound from a stream comprising the first chemical component orcompound and one or more other chemical components, compounds, or thelike. Non-limiting examples of suitable absorption reactors and/orabsorption reactor configurations include an absorption (distillation)tower, a pressure-swing absorption (PSA) configuration, a sparger tank,an agitation reactor, one or more compressors, one or more recyclepumps, or combinations thereof.

In an embodiment, the absorption reactor may be configured to dissipatea gas within a liquid (e.g., by bubbling the gas through the liquid).For example, in an embodiment, the absorption reactor 116 may include asolvent circulation system configured to circulate solvent through theabsorption reactor 116. The solvent circulation flow rate may bedetermined by the operating conditions of the absorption system, as isdisclosed herein below. In an embodiment, the absorption reactor 116 maycomprise and/or be in fluid communication with one or more pumpsconfigured to recirculate solvent via and/or within the absorptionreactor 116. In an additional and/or alternative embodiment, theabsorption reactor 116 may comprise a packed bed or column configured tomaintain smaller bubble sizes (e.g., of the gas being dissipated withinthe liquid), for example, so as to maintain a relatively large surfacearea of contact between the gas and the liquid, for example, so as tomaintain an efficiency of mass transfer and/or absorption of the gasinto the liquid. In an embodiment, the packing material of the packedbed or column may comprise a polymeric material, metallic material, orcombinations thereof. In an embodiment, the absorption reactor 116 mayhave multiple packed beds or columns. In an embodiment, only a sectionof the absorption reactor 116 may have a packing material. In anembodiment, the packing material of a packed absorption reactor 116 mayhave a random packing or may have a structured packing. An example of asuitable absorption reactor is illustrated in the Gas ProcessorsAssociation, “Engineering Data Book” 10^(th) ed. at FIG. 19-16.

In an embodiment where the absorption reactor 116 comprises a solventreactor, the absorption reactor may comprise a suitable absorptionsolvent system, as will be disclosed herein. Such an absorption reactor116 may be configured to retain the absorption solvent system. Forexample, the absorption solvent system may be retained within thereactor as a liquid, as a fixed bed, or as a fluidized bed.

In an embodiment, a suitable absorption solvent system may be capable ofreversibly complexing with the ethylene and/or isobutane. Such anabsorption solvent system may generally comprise a complexing agent anda solvent. In an embodiment, an absorption solvent system may becharacterized as having a selectivity of ethylene to ethane whereethylene and ethane are present at the same partial pressure of about40:1 at approximately 14 psi, about 12:1 at approximately 20 psi, about6:1 at approximately 40 psi, and about 3:1 at approximately 180 psipartial pressure. In an embodiment, the solvent system may be furthercharacterized as having a high contaminant tolerance and as exhibitinghigh stability at increased and/or fluctuating temperatures and/orpressures, or combinations thereof.

In an embodiment, the complexing agent may comprise a metallic salt. Insuch an embodiment, the metallic salt may comprise a salt of one or moretransition metals and a weakly-ionic halogen. Non-limiting examples ofsuitable transition metals include silver, gold, copper, platinum,palladium, or nickel. Non-limiting example of suitable weakly-ionichalogens include chlorine and bromine. In an embodiment, a suitabletransition metal salt may be characterized as having a high specificityfor olefins. Non-limiting examples of suitable transition metal-halogensalts include silver chloride (AgCl) and copper chloride (CuCl). In aparticular embodiment, the salt employed in the absorption solventsystem comprises CuCl. Not seeking to be bound by theory, such ametallic salt may interact with the double carbon bonds of olefins(e.g., ethylene).

In an embodiment, the complexing agent may comprise a copper (I)carboxylate. In such an embodiment, suitable copper (I) carboxylates maycomprise salts of copper (I) and mono-, di-, and/or tri-carboxylic acidscontaining 1-20 carbon atoms. The carboxylic acid component of the saltmay comprise an aliphatic constituent, a cyclic constituent, an arylconstituent, or combinations thereof. Other suitable examples of copper(I) carboxylates include Cu(I) formate, Cu(I) acetate, Cu(I) propionate,Cu(I) butyrate, Cu(I) pentanoate, Cu(I) hexanoate, Cu(I) octanoate,Cu(I) decanoate, Cu(I) 2-ethyl-hexoate, Cu(I) hexadecanoate, Cu(I)tetradecanoate, Cu(I) methyl formate, Cu(I) ethyl acetate, Cu(I)n-propyl acetate, Cu(I) n-butyl acetate, Cu(I) ethyl propanoate, Cu(I)octoate, Cu(I) benzoate, Cu(I) p-t-butyl benzoate, and the like. In anadditional embodiment, the complexing agent may comprise an adduct of acopper (I) carboxylate, for example, as disclosed herein, and borontrifluoride (BF₃).

In an additional and/or alternative embodiment, the complexing agent maycomprise a copper (I) sulfonate. Non-limiting examples of suitablecopper (I) sulfonates include the copper (I) salts of sulfonic acidshaving 4 to 22 carbon atoms. The sulfonic acid component of the salt maycomprise an aliphatic constituent, a cyclic constituent, an arylconstituent, or combinations thereof. The aliphatic sulfonic acids canbe straight chain or branched. Examples of suitable aliphatic sulfonicacids include, but are not limited to, n-butanesulfonic acid,2-ethyl-1-hexanesulfonic acid, 2-methylnonanesulfonic acid,dodecanesulfonic acid, 2-ethyl-5-n-pentyltridecanesulfonic acid,n-eicosanesulfonic acid, and the like. Examples of suitable aromaticsulfonic acids include benzenesulfonic acid, alkylbenzenesulfonic acidswherein the alkyl member contains from 1 to 16 carbon atoms, such asp-toluenesulfonic acid, dodecylbenzenesulfonic acid (o-, m-, and p-),p-hexadecylbenzenesulfonic acid, and the like, naphthalenesulfonic acid,phenolsulfonic acid, naphtholsulfonic acids, and halobenzenesulfonicacids, such as p-chlorobenzenesulfonic acid, p-bromobenzenesulfonicacid, and the like.

In an embodiment where the complexing agent may further comprise ahindered olefin. For example, the complexing agent may comprise such ahindered olefin in an embodiment wherein the complexing agent forms acopper complex with insufficient solubility. An example of such ahindered olefin is a propylene tetramer (i.e. dodecene). Not intendingto be bound by theory, the hindered olefin may increase the solubilityof the copper complex while being easily displaced by ethylene.

In various embodiments, the complexing agent may comprise one or more ofthe complexing agents disclosed in U.S. Pat. Nos. 5,104,570; 5,191,153;5,259,986; and 5,523,512, each of which is incorporated by reference inits entirety.

In an embodiment, the solvent may comprise an amine or an amine complex,an aromatic hydrocarbon, an olefin, or combinations thereof.Non-limiting examples of solvent amines include pyridine, benzylamine,and aniline. For examples, the amine may comprise an aniline(phenylamine, aminobenzene); alternatively, aniline combined withdimethylformamide (DMF), and in embodiments, aniline andN-methylpyrrolidone (NMP). In an embodiment where the solvent comprisesan aromatic hydrocarbon, the aromatic hydrocarbon may comprise anunsubstituted or alkyl substituted aryl groups. In such an embodiment,the aromatic hydrocarbon may be in the liquid phase under normal,ambient conditions. Suitable non-limiting examples include toluene,xylene, and the like. In embodiments where the solvent comprises anolefin, non-limiting examples include olefins having 10 to 16 carbonatoms. For example, the olefin may comprise propylene tetramer,dodecene, tetradecene, hexadecene, or combinations thereof.

In an embodiment, the solvent may be characterized as aprotic, that is,as not including a dissociable hydrogen atom. Not intending to be boundby theory, a dissociable hydrogen solvent may result in thehydrogenation of the double bond between carbons in an olefin such asethylene. Further, the solvent may be characterized as polar, as havinga slight polarity, or as having unidirectional, electric charge. Notintending to be bound by theory, a polar solvent may interact with andat least partially solubilize the salt.

In an embodiment, the solvent may be characterized as a liquid producedindustrially in relatively high volumes, having a relatively low cost,being easily transportable, or combinations thereof. The solvent may befurther characterized as capable of retaining a complexed olefin-metalsalt or retaining a weakly ionic metal salt despite fluctuations intemperature and/or pressure.

In an embodiment, the absorption solvent system may comprise copperchloride, aniline, and dimethylformamide (CuCl/aniline/DMF). In analternative embodiment, the absorption solvent system may comprisecopper chloride, aniline, and N-methylpyrrolidone (CuCl/aniline/NMP). Insuch an embodiment, a CuCl/aniline/NMP solvent system may becharacterized as having increased volatile stability at lower pressuresand higher temperatures. In alternative embodiments, the absorptionsolvent system may comprise copper (I) carboxylate and an aromaticsolvent such as toluene or xylene. In alternative embodiments, theabsorption solvent system may comprise copper (I) sulfonate and anaromatic solvent such as toluene or xylene. In alternative embodiments,the absorption solvent system may comprise an adduct of copper (I)carboxylate and BF₃ in an aromatic solvent such as toluene or xylene.

In an embodiment, the absorption solvent system may comprise copper (I)2-ethyl-hexanoate and propylene tetramer. In an embodiment, theabsorption solvent system may comprise copper (I) 2-ethyl-hexanoate anddodecene. In an embodiment, the absorption solvent system may comprisecopper (I) hexadecanoate and hexadecene. In an embodiment, theabsorption solvent system may comprise copper (I) tetradecanoate andtetradecene.

In an embodiment, allowing the at least one component to be absorbed bythe absorbent may comprise allowing the at least one component to becomereversibly bound, linked, bonded or combinations thereof to theabsorbent or a portion thereof, for example, via the formation ofvarious links, bonds, attractions, complexes, or combinations thereof.For example, in an embodiment where the absorbent comprises anabsorption solvent system (e.g., a CuCl/aniline/DMF solvent system or aCuCl/aniline/NMP solvent system), allowing absorption of the at leastone component may comprise allowing a complex to form between theabsorbent and the at least one component, referred to as an absorbedcomponent complex (e.g., an absorbed ethylene complex).

Allowing absorption of the at least one component may further compriseproviding and/or maintaining a suitable pressure of the environment inwhich the gas stream and absorbent are brought into contact, providingand/or maintaining a suitable partial pressure of a gas, providingand/or maintaining a suitable temperature in the environment in whichthe gas stream and absorbent are brought into contact, catalyzing theabsorption, or combinations thereof. Not intending to be bound bytheory, the absorption of the at least one component by the absorbentmay be improved at a suitable temperature and/or pressure.

In an embodiment, the absorption reactor 116 may be capable ofselectively inducing thermal and/or pressure fluctuations, variations,or cycles. In an embodiment, the absorption reactor 116 may beconfigured to selectively absorb and/or induce the absorption of anunreacted ethylene monomer (and optionally, comonomer) from acomposition comprising various other gases (e.g., ethane). In anotherembodiment, the absorption reactor 116 may be configured to selectivelyabsorb and/or induce the absorption of butane, particularly, isobutane,from a composition comprising various other gases. In still anotherembodiment, the absorption reactor 116 may be configured to selectivelyabsorb both unreacted ethylene and butane, particularly, isobutane, froma composition comprising various other gases (e.g., ethane).

In an embodiment, the absorption reactor 116 may be configured toprovide or maintain a suitable temperature, for example, as may bedependent upon the phase in which the absorption reactor operates at agiven time. For example, the absorption reactor 116 may be configured toprovide or maintain a suitable temperature, for example, for the purposeof increasing absorption of a desired chemical species, decreasingabsorption of a desired chemical species, flashing an unabsorbed gasfrom the reactor 116, recovering unreacted ethylene from the absorptionreactor 116, regenerating absorbent in the absorption reactor 116, orcombinations thereof. In an embodiment, such a suitable temperature maybe in a range of from about 40° F. to about 110° F., alternatively, fromabout 40° F. to about 60° F., alternatively, from about 45° F. to about55° F., alternatively, from about 50° F. to about 55° F., alternativelyabout 50° F. For example, it has been found the operating temperature ofthe absorption reactor 116 (and absorption solvent system) in atemperature range of from about 40° F. to about 110° F., alternatively,from about 40° F. to about 60° F., alternatively about 50° F. may yieldan unexpected increase in the absorption of ethylene relative to theabsorption of ethane. Not intending to be bound by theory, one skilledin the art will appreciate (for example, based on partial pressureconcepts from Raoult's law) the expectation for solubility of ethyleneand ethane in an absorbent solvent to increase at decreasingtemperatures. However, contrary to such expectations, it has been foundthat the amount of ethylene absorbed in the absorbent solvent and/or theabsorbent solvent system of the disclosed embodiments decreases as thetemperature decreases below 50° F. Because of this unexpectedphenomenon, absorption of ethylene may be greatest for temperatures in arange of from about 40° F. to about 110° F., alternatively, in a rangeof from about 40° F. to about 60° F., alternatively, at a temperature ofabout 50° F. FIG. 7 is graph showing the solubility at varyingtemperatures for ethylene and ethane in a copper chloride, aniline, NMPabsorbent solvent system. The graph illustrates the expected solubilitytrend of ethane and the unexpected solubility trend of ethylene acrossthe temperatures discussed above.

In an embodiment, the absorption reactor 116 may be configured toprovide or maintain a suitable temperature in a range from about 40° F.to about 110° F. during absorption of one or more components of the gasstream (e.g., ethylene and/or isobutane). As disclosed above, it hasbeen found that ethylene solubility is unexpectedly greatest attemperature in a range of from about 40° F. to about 60° F. In anembodiment, the absorption reactor 116 may be operated at a temperatureof from about 40° F. to about 60° F., alternatively a temperature ofabout 50° F. during absorption of ethylene and/or isobutene from a gasstream. In an alternative embodiment, the absorption reactor may beoperated at a temperature of from about 60° F. to about 110° F., or fromabout 70° F. to about 90° F. during absorption of ethylene and/orisobutene from a gas stream. For example, such absorption temperaturesof the absorption reactor 116 may be suitable as an economic alternativeto operating at a lower temperature (which may require energyexpenditure with cooling, for example). For example, operating anabsorption reactor, like absorption reactor 116, at temperatures in arange of from about 60° F. to about 110° F., or from about 70° F. toabout 90° F. may require less energy, which may create a cost savings,by allowing the absorption reactor to be operated at the ambienttemperature of a given geographic location.

In an embodiment, the absorption reactor 116 may be configured toprovide or maintain a suitable pressure during operation. Such asuitable pressure may be in a range of from about 5 psig to about 500psig, alternatively, from about 50 psig to about 450 psig,alternatively, from about 75 psig to about 400 psig. In an additionalembodiment, the absorption reactor 116 may be configured to provide ormaintain a suitable partial pressure of ethylene during operation. Sucha suitable ethylene partial pressure may be in a range of from about 1psia to about 400 psia, alternatively, from about 30 psia to about 200psia, alternatively, from about 40 psia to about 250 psia,alternatively, from about 40 psia to about 75 psia, alternatively, fromabout 40 psig to about 60 psig, alternatively about 40 psig,alternatively, about 60 psig. Not intending to be bound by theory,pressurizing the absorption reactor 116 may facilitate absorption ofethylene and/or the formation of a complex of ethylene and theabsorption solvent system (e.g., the CuCl/aniline/NMP system). Also, notintending to be bound by theory, the selectivity of the absorptionsolvent system for ethylene may increase with a decrease in the pressureof the absorption reactor.

In an embodiment, the absorption reactor 116 may be configured for batchand/or continuous processes. For example, in an embodiment, a PEP systemmay comprise two or more absorption reactors (e.g., such as absorptionreactor 116), each of which may be configured for batch operation. Forexample, by employing two or more absorption reactors, such a system maybe configured to allow for continuous operation by absorbing a componentof a gas stream into a “first batch” in the first absorption reactorwhile a “second batch” is prepared for absorption in the secondabsorption reactor. As such, by cycling between two or more suitablereactors, a system may operate continuously.

For example, in an embodiment two or more absorption reactors (e.g., anabsorption reactor system) may be configured for pressure swingabsorption (PSA) of ethylene using a liquid solvent, for example, theabsorption solvent system or absorption solvent as disclosed herein. Insuch an embodiment, the absorption reactor 116 may include two or moreabsorption reactors configured for PSA (e.g., an absorption reactorsystem). FIG. 8, shows an absorption reactor system 800 with fourabsorption reactors 810, 820, 830, and 840 configured for PSA. Althoughthe embodiment of FIG. 8 illustrates four absorption reactors (e.g.,absorption reactors 810, 820, 830, and 840), one of skill in the art,upon viewing this disclosure, will recognize that two, three, five, six,seven, eight, or more absorption reactors may be similarly employed. Insuch an embodiment, the each of the absorption reactors may beconfigured substantially as disclosed herein. In an embodiment, one ormore of the reactors 810, 820, 830, and 840 may be connected via acirculation system (for example, comprising one or more pumps, valves,conduits, and the like) to circulate the liquid solvent in the reactors810, 820, 830, and 840 during absorption. The absorption reactors 810,820, 830, and 840 may cycle between an absorption phase (in which agaseous component, such as ethylene and/or isobutane, is absorbed by theabsorption solvent and/or absorption solvent system) and a regenerationphase (in which the absorbed and/or complexed gaseous component isliberated from the absorption solvent system and/or the absorptionsolvent system is prepared for reuse, as will be disclosed herein). Forexample, the reactors 810, 820, 830, and 840 may be cycled between theabsorption and regeneration phases (e.g., via one or more intermediatephases) on a coordinated basis so that not all reactors 810, 820, 830,840 are undergoing absorption or regeneration at the same time. In anembodiment where absorption reactors 810, 820, 830, and 840 areconfigured to operate in PSA, the reactors 810, 820, 830, and 840 serveas both absorbers and as regenerators. In such an embodiment, separatevessels for regeneration may not be required (e.g., as disclosedherein).

As an example of PSA operation on a coordinated basis, at a given phaseduring such operation, reactor 810 may operate in the absorption phase,for example, at absorption conditions as disclosed herein. Atsubstantially the same time, reactor 820 may be pressurized to anintermediate pressure, for example, below that of the absorptionpressure. Also, at substantially the same time, reactor 830 maydepressurize from an intermediate pressure to a regeneration pressure,and while reactor 840 may depressurize from an absorption pressure (frompreviously being in an absorption phase) to an intermediate pressure.Not intending to be bound by theory, depressurization (e.g., from theabsorption pressure to the intermediate pressure and from theintermediate pressure to the regeneration pressure) of each of reactors810, 820, 830, and/or 840 following absorption may allow the absorbedgaseous components (e.g., ethylene and/or isobutane) to be liberatedfrom the absorbent and/or the absorbent to be regenerated (e.g.,prepared for re-use, as disclosed herein). In an embodiment, thepressure from one or more of the reactors (e.g., reactors 810, 820, 830,and/or 840) may be utilized to pressurize another of these reactors. Forexample, in the embodiment of FIG. 8, the pressure of gas in reactor 840may be used to pressurize reactor 820 to the intermediate pressurethrough line 850, with valves 858 and 884 being in an open position andvalves 882 and 856 being in a closed position. Valves 862, 864, 866, and868 may be switched between an open position and a closed position toallow product nitrogen in stream 860 to flow in and out of reactors 810,820, 830, and 840. Valves 852, 854, 856, 858 may be switched between anopen position and a closed position to allow pressurization anddepressurization of reactors 810, 820, 830, and 840 through stream 850.Valves 882, 884, 886, 888 may be switched between an open position and aclosed position to allow light gas stream 880 to feed to reactors 810,820, 830, and 840 when in the absorption phase. Valves 892, 894, 896,and 898 may be switched between an open position and a closed positionto remove any purge gas from reactors 810, 820, 830, and 840 throughstream 890.

In an embodiment, a stripping gas, such as isobutane or nitrogen, may beadded to the absorption reactors 810, 820, 830, and 840, for example,through stream 870 during the regeneration phase. Stream 870 may bepositioned at a bottom of reactors 810, 820, 830, and 840 so thestripping gas may bubble through the reactor 810, 820, 830, or 840 (andthrough any packing materials therein). Valves 872, 874, 876, and 878may be switched between open and closed positions to add the strippinggas to the reactors 810, 820, 830, and 840 during regeneration. Notintending to be bound by theory, the stripping gas may lower the partialpressure of ethylene in the absorption reactors 810, 820, 830, and 840during regeneration.

In an embodiment, one or more of the absorption reactors 810, 820, 830,and 840 may comprise internals to distribute the gas through the liquidabsorption solvent and prevent channeling. Suitable internals mayinclude distillation packing that distributes gas and reduces axialmixing of the liquid. Internals may prevent liquid absorption solvent inthe absorption reactors 810, 820, 830, and 840 from mixing so thatsolvent flow would be first saturated and then a saturation front maymove vertically upward through the absorption reactors 810, 820, 830,and 840.

In an embodiment, separating at least one gaseous component from the gasstream comprises removing a waste stream. In an embodiment, theremaining unabsorbed gas stream components form the waste stream. In anembodiment where the absorbed component comprises ethylene and theabsorbent comprises a CuCl/aniline/DMF or a CuCl/aniline/NMP solventsystem, such a waste stream may comprise methane, ethane, acetylene,propylene, various other hydrocarbons, volatile contaminants, orcombinations thereof. Further, such a waste stream may be substantiallyfree of unreacted ethylene monomers or, optionally, comonomers. As usedherein, “substantially free of unreacted ethylene monomers” means thatthe waste gases comprise less than 50% unreacted ethylene monomers,alternatively, less than 10% unreacted ethylene monomers, alternatively,less than 1.0% unreacted ethylene monomers, alternatively, less than 0.1unreacted ethylene monomers, alternatively, less than 0.01% unreactedethylene monomers by total weight of the stream.

In an embodiment, removing the waste stream may comprise cooling thewaste stream, and/or reducing or increasing the waste stream pressuresuch that the waste stream flows to the processing device 114. Forexample, in an embodiment, the waste stream may be “swept away” byconveying a suitable sweep gas (e.g., an inert or unreactive gas, asdisclosed above) through the vessel containing the waste gas (e.g., theabsorption reactor 116) at a sufficient pressure, at velocity, orcombinations thereof to expel the waste gases therefrom. For example, inthe embodiments illustrated by FIGS. 1-3, separating at least onegaseous component from the gas stream yields a waste gas stream 20 beingsubstantially free of unreacted ethylene monomers (optionally,comonomers), alternatively, a waste gas stream having a reducedconcentration of unreacted ethylene monomers (optionally, comonomers).For example, the waste gas stream may comprise less than about 30%,alternatively, less than about 25%, alternatively, less than about 20%,alternatively, less than about 15%, alternatively, less than about 10%unreacted ethylene monomers by total weight of the stream. In anadditional embodiment, the ethylene may be decreased by a percentage ofthe ethylene present in the gas stream prior to separating at least onegaseous component therefrom. For example, the waste gas stream maycomprise less than about 40%, alternatively, less than about 30%,alternatively, less than about 20% by total weight of the stream of theunreacted ethylene monomers present in the gas stream prior toseparation.

In an embodiment, separating at least one gaseous component from the gasstream may further comprise liberating the absorbed gaseous componentfrom the absorbent (e.g., in situ within absorption reactor 116 and/orin another vessel such as regenerator 120). Liberating the absorbedgaseous component from the absorbent generally comprises any suitablemeans of reversing the various links, bonds, attractions, complexes, orcombinations thereof by which the at least one gaseous component isbound, linked, bonded or combinations thereof to the absorbent or aportion thereof. Nonlimiting examples of a suitable means by which toliberate the absorbed gaseous component include altering absorptionkinetics or the absorption equilibrium of the absorbent, heating ordepressurizing the absorbent, altering the partial pressure of theabsorbed gas, or combinations thereof.

In an embodiment, the absorbed gaseous component may be liberated (e.g.,desorbed and/or decomplexed) from the absorbent within the one or moreof such absorption reactors in a regeneration and/or desorption phase.For example, in the embodiment of FIGS. 1 and 2 (and/or, in anembodiment where the absorption reactor 116 is configured in a PSAconfiguration, as disclosed herein with respect to FIG. 8), theabsorption reactor 116 may be configured to induce the release of thegas absorbed or complexed by the absorption solvent therefrom (e.g.,desorption and/or decomplexation of the absorbed and/or complexedethylene and/or isobutane), as disclosed in detail herein. Not intendingto be bound by theory, inducing the release of the absorbed or complexedgas may comprise altering the reaction kinetics or the gas-solventequilibrium of the absorption solvent system, the temperature of theabsorption reactor 116, the pressure of the absorption reactor 116, thepartial pressure of the absorbed gas, or combinations thereof. In suchan embodiment, the absorption reactor 116 may comprise controls, thermalconduits, electric conduits, compressors, vacuums, the like, orcombinations thereof configured to alter the reaction kinetics, thegas-solvent equilibrium, the temperature of the absorption reactor 116,the pressure of the absorption reactor 116, or combinations thereof.

For example, in an embodiment, liberating the absorbed gaseous componentmay comprise depressurizing the solution comprising the complexedethylene to a suitable partial pressure. In an additional embodiment,liberating the absorbed gaseous component may comprise heating hesolution comprising the complexed ethylene within the absorption reactor116 (alternatively, within a regenerator 120, as disclosed herein below)to a suitable temperature. Such a suitable temperature may be in a rangeof from about 110° F. to about 200° F., alternatively, from about 140°F. to about 160° F., alternatively, from about 160° F. to about 200° F.,alternatively, from about 180° F. to about 200° F., to encourage releaseof the absorbed compound (e.g., ethylene and/or isobutane) from theabsorption solvent. For example, in a particular embodiment, theabsorption reactor 116 (alternatively, the regenerator 120) may beoperated at a temperature of from about 160° F. to about 200° F.,alternatively, from about 180° F. to about 200° F. during the liberationof the absorbed component (e.g., ethylene and/or isobutene) from theabsorption solvent. In an alternative embodiment, the absorption reactor116 (alternatively, the regenerator 120) may be operated at atemperature of from about 140° F. to about 160° F. during the liberationof the absorbed component (e.g., ethylene and/or isobutene) from theabsorption solvent. For example, such liberation temperatures may besuitable as an economic alternative. For example, operation anabsorption reactor like absorption reactor 116 (alternatively, aregenerator like regenerator 120) at temperatures in a range of fromabout 140° F. to about 160° F. during the liberation of the absorbedcomponent may require less energy, which may create a cost savings, byallowing heat derived from other sources (e.g., polymerization reactorcoolant, low pressure stream, heat-exchangers upstream of regenerators,heat-exchangers in the absorbent recycle line, polymerization reactors,flash-line heaters, flash vessels, or the like, or combinations thereof)to be utilized to heat the absorption reactor and/or the regenerator.

Additionally, in such an embodiment, the absorption reactor 116 may beconfigured to evacuate gases (e.g., a previously absorbed and thenreleased gas, such as ethylene) and/or to facilitate the release of theabsorbed gas via a pressure differential. The absorption reactor 116 maybe configured to provide or maintain a suitable partial pressure. Such asuitable partial pressure may be in a range of from about 0.1 psig toabout 40 psig, alternatively, from about 5 psig to about 30 psig,alternatively, from about 5 psig to about 15 psig. In an embodiment, theabsorption reactor 116 may be configured to provide or maintain anethylene partial pressure in a range of from about 0 psia to about 5psia.

In an alternative embodiment, separating at least one gaseous componentfrom the gas stream may further comprise removing the solutioncomprising the absorbed component complex (e.g., the absorbed ethylenecomplex) for further processing. In such an alternative embodiment, theabsorption complex comprising the absorbed gaseous component may beremoved from the absorption reactor 116 to the regenerator 120 forliberation of the absorbed gaseous component and/or regeneration of theabsorption complex as a complexed stream 28. In such an embodiment, thecomplexed stream 28 may comprise ethylene, ethane, and/or isobutane.Ethylene may be present in a range of from about 0.1% to about 10%,alternatively, from about 0.4% to about 5%, alternatively, from about0.5% to about 2.5% by total weight of the stream. Ethane may be presentin a range of from about 0.1% to about 1%, alternatively, from about0.2% to about 0.5% by total weight of the stream. Isobutane may bepresent in a range of from about 0.1% to about 1%, alternatively, fromabout 0.2% to about 0.5% by total weight of the stream.

In one or more of the embodiments disclosed herein, separating acomplexed stream into a recycle stream and an absorbent stream (e.g., atblock 58) comprises liberating the absorbed gaseous component from theabsorbent. As explained above, liberating the absorbed gaseous componentfrom the absorbent generally comprises any suitable means for reversingthe various links, bonds, attractions, complexes, or combinationsthereof by which the at least one gaseous component is bound, linked,bonded or combinations thereof to the absorbent or a portion thereof.Various processes and/or parameters for liberating an absorbed gaseouscomponent were disclosed above with respect to liberation within theabsorption reactor.

In the embodiment illustrated by FIG. 3, separating a complexed streaminto a recycle stream and an absorbent stream may comprise routing thecomplexed stream 28 to the regenerator 120. In one or more one or moreof the embodiments disclosed herein, a regenerator 120 may comprise adevice or apparatus configured to recover, regenerate, recycle, and/orpurify an absorption solvent and/or to liberate an absorbed gas.Non-limiting examples of a suitable regenerator include a flash reactor,a depressurization reactor, a solvent regeneration reactor, orcombinations thereof.

In an embodiment, regenerator 120 may be configured to operate on thebasis of a pressure differential. In such an embodiment, the regenerator120 may be configured to provide or maintain a suitable internalpressure. Such a suitable internal pressure may be in a range of fromabout 0 psig to about 150 psig, alternatively, from about 5 psig toabout 30 psig, alternatively, from about 5 psig to about 15 psig,alternatively, from about 0 psig to about 10 psig. In an embodiment, theregenerator 120 may be configured to provide or maintain a suitablepartial pressure. Such a suitable partial pressure may be in a range offrom about 0 psia to about 50 psia.

In an embodiment, regenerator 120 may be configured to operate on thebasis of an elevated temperature. Such a regenerator 120 may beconfigured to provide or maintain a suitable temperature. Such asuitable temperature may be in a range of from about 110° F. to about200° F., alternatively, from about 140° F. to about 200° F.,alternatively, from about 140° F. to about 160° F., alternatively, fromabout 160° F. to about 200° F., alternatively, from about 180° F. toabout 200° F., to vaporize and/or release an absorbed compound (e.g.,ethylene and/or isobutane) from the absorption solvent. In anembodiment, regenerator 120 (e.g., like the absorption reactor 116) maybe heated to desorb, or regenerate, the absorption solvent system usingheat sources comprising cooling water, low-pressure steam, orcombinations thereof. Cooling water, low pressure steam, or acombination thereof may be suitable for heating regenerator 120 (or theabsorption reactor 116, as disclosed above) to a temperature of fromabout 140° F. to about 200° F.

In an embodiment, the regenerator 120 may be configured for batch and/orcontinuous processes. For example, in an embodiment, a PEP system maycomprise two or more absorption regenerators (e.g., such as regenerator120), each of which may be configured for batch operation. As explainedabove, by employing two or more absorption reactors, such a system mayoperate to regenerate the absorbent continuously.

In an embodiment, separating a complexed stream into a recycle streamand an absorbent stream may yield a regenerated absorbent steam whichmay be reused in an absorption reaction and a recycle stream comprisingunreacted monomers (optionally, comonomers) which may be reintroducedinto or reused in a PEP process. For example, in the embodimentillustrated by FIG. 3, separating a complexed stream into a recyclestream and an absorbent stream 58 yields a recycle stream 22 which maybe returned to the purifier 102 and a regenerated absorbent stream 30which may be returned to the absorption reactor 116.

In an embodiment, liberating the absorbed gas may also yield a recyclestream comprising unreacted monomers (optionally, comonomers) which maybe returned to the separator 108 for pressurization (e.g., via one ormore compressors located at the separator 108). For example, in theembodiments illustrated by FIGS. 1-3, liberating the absorbed gas yieldsa recycle stream 22 which may be returned to the separator 108.Pressurizing the recycle stream 22 may yield a reintroduction stream 24which may be reintroduced into or reused in a PEP process. For example,in the embodiments illustrated by FIGS. 1-3, a reintroduction stream 24is introduced into the purifier 102. In an alternative embodiment, arecycle stream (such as recycle stream 22) may be pressurized and/orreintroduced into a PEP process without being returned to the separator108. In an embodiment, the recycle stream 22 may comprise substantiallypure ethylene; alternatively, the recycle stream 22 may compriseethylene and butane, particularly, isobutane. In an embodiment, the gasstream may comprise may comprise nitrogen, ethylene, ethane, and/orisobutane. Ethylene may be present in a range of from about 65% to about99%, alternatively, from about 70% to about 90%, alternatively, about75% to about 85% by total weight of the stream. Ethane may be present ina range of from about 1% to about 20%, alternatively, from about 5% toabout 15%, alternatively, from about 7.5% to about 12.5% by total weightof the stream. Isobutane may be present in a range of from about 1% toabout 20%, alternatively, from about 5% to about 15%, alternatively,from about 7.5% to about 12.5% by total weight of the stream.

In one or more one or more of the embodiments disclosed herein,combusting a waste gas stream (e.g., at block 56) may generally compriseburning or incinerating one or more gaseous components of the waste gasstream 20. In one or more of the embodiments disclosed herein,combusting the waste gas stream 20 may further or alternatively comprisecracking, catalytic cracking, pyrolysis, dehydrogenating, scrubbing,converting, treating, or combinations thereof, of the waste gas stream20 or combustion products.

As disclosed herein, the waste gas stream 20 may comprise volatilizedsolvents, unreacted gases, secondary products, contaminants,hydrocarbons, or combinations thereof. In an embodiment, the waste gasstream 20 may comprise hydrogen, nitrogen, methane, ethylene, ethane,propylene, propane, butane, isobutane, heavier hydrocarbons, orcombinations thereof. Ethylene may be present in a range of from about1% to about 40%, alternatively, from about 2.5% to about 20% by totalweight of the stream. Ethane may be present in a range of from about 5%to about 50%, alternatively, from about 30% to about 40% by total weightof the stream. Isobutane may be present in a range from about 1% toabout 20%, alternatively, from about 1.5% to about 5%, alternatively,from about 2% to about 3% by total weight of the stream. Nitrogen may bepresent in a range from about 10% to about 80%, alternatively, fromabout 35% to about 50%, alternatively, from about 40% to about 45% bytotal weight of the stream.

In embodiments as illustrated by FIGS. 1-3, combusting waste gas streammay comprise routing the waste gas stream 20 to the processing device114. In one or more of the embodiments disclosed herein, the processingdevice 114 may comprise a combustion device or apparatus, such as aflare. Nonlimiting examples of a suitable flare include a torch,incinerator, the like, or combinations thereof. A flare may suitablycomprise one or more controllable nozzles, an ignition source, a bypassvalve, a pressure relief valve, or combinations thereof. The flare maybe configured to provide an environment for the combustion of variouswaste products, for example, atomic gases (e.g. nitrogen, oxygen),oxides (e.g. carbon monoxide, oxides of nitrogen or sulfur), variousunwanted gaseous products, or combinations thereof. In an embodiment,the flare may additionally comprise a device or apparatus configured toselectively remove one or more of contaminants prior to, during, and/orafter combustion (e.g., such that a given combustion product is notreleased into the atmosphere).

In one or more of the embodiments disclosed herein, the processingdevice 114 may comprise a cracker, catalytic cracker, scrubber,converter, treater, dehydrogenator, deoxygenator, or combinationsthereof, for example. In an embodiment, processing device 114 maycomprise an ethylene cracker. In the processing device 114, one or moregaseous components, such as ethane, from waste gas stream 20 may beconverted to a desired product, such as ethylene monomer. The desiredproduct formed in the processing device 114 may be recycled to one ormore of purifier 102, reactor 104, reactor 106, for example.

In other alternative embodiments, waste gas stream 20 may be used asfuel (for example for steam generation or co-gen operations, and/or maybe used as fuel and/or a feed to a thermal cracking unit to formethylene (e.g., to form feed stream 10). In another alternativeembodiment, the waste gas from waste gas stream 20 may be exported fromthe plant to a monomer plant.

In an embodiment, implementation of one or more of the disclosed systems(e.g., PEP systems 100, 200, and/or 300) and/or processes (e.g., PEPprocesses 400, 500, and/or 600) may allow for the recovery of asubstantial portion of the ethylene monomers that would otherwise belost due to the operation of such systems or processes, for example, byflaring. In an embodiment, one or more of the disclosed systems mayallow for the recovery of up to about 75%, alternatively, up to about85%, alternatively, up to about 90%, alternatively, up to about 95% bytotal weight of the stream of the ethylene monomers that would otherwisebe lost. In an embodiment, one or more of the disclosed systems mayallow for the recovery of up to about 75%, alternatively, up to about85%, alternatively, up to about 90%, alternatively, up to about 95% bytotal weight of the stream of the isobutane that would otherwise belost. The recovery of such a portion of the unreacted ethylene monomersmay yield a significant economic benefit, for example, by improving theefficiency of usage of ethylene monomers and decreasing capital inputsassociated with the acquisition of ethylene monomers. Similarly, therecovery of such a portion of isobutane may yield a significant economicbenefit, for example, by decreasing capital inputs associated with theacquisition of isobutane and/or by reducing the presence of isobutane inflare emissions.

In an embodiment, implementation of one or more of the disclosed systemsand/or processes may decrease the amount of ethane that is returned to apolymerization reactor (such as reactors 104 and/or 106) via a recyclestream. By decreasing the amount of ethane contained in a streamrecycled to a polymerization reactor, the overall efficiency of thepolyethylene production may be improved (for example, by increasing theethylene concentration without reaching the bubble point in the loopreactor). For example, decreasing the amount of ethane in a recycledstream may improve polymerization reactor efficiency, improve catalystefficiency, reduce polymer fouling, reduce polymerization downtime, orcombinations thereof.

A skilled artisan will recognize that industrial and commercialpolyethylene manufacturing processes may necessitate one or more, oftenseveral, compressors or similar apparatuses. Such compressors are usedthroughout polyethylene manufacturing, for example to pressurizereactors 104, 106 during polymerization. Further, a skilled artisan willrecognize that a polyethylene manufacturing process includes one or moredeoxygenators and/or similar de-oxidizing apparatuses, for instancepurifying solvents or reactants and/or for purging reactors of oxygen.Because the infrastructure and the support therefore, for example toprovide power and maintain the compressors and/or deoxygenators, alreadyexists within a commercial polyethylene manufacturing plant,reallocating a portion of these available resources for use in thedisclosed systems may necessitate little, if any, additional capitalexpenditure in order to incorporate the disclosed systems and orprocesses.

Further, because compressors, deoxygenators, and various othercomponents are already employed in various polyethylene processes andsystems, the opportunity for increased operation of such apparatuses mayimprove the overall efficiency of polyethylene production systems andprocesses. For example, when a portion of a PEP process or system istaken off-line for maintenance and/or repair, other portions of thesystem (e.g., a compressor, a deoxygenator, a reactor, etc.) maycontinue to provide service according to the current processes.Operating and/or reallocating resources for operation of the disclosedPEP systems and/or processes may thereby increase the efficiency withwhich conventional systems are used.

ADDITIONAL DESCRIPTION

A process and system for the production for polyethylene has beendescribed. The following clauses are offered as further description:

Embodiment A. A process for recovery of ethylene from a polymerizationproduct stream of a polyethylene production system, comprising:

separating a light gas stream from the polymerization product stream,wherein the light gas stream comprises ethane and unreacted ethylene;

contacting the light gas stream with an absorption solvent system,wherein the contacting the light gas stream with the absorption solventsystem occurs at a temperature in a range of from about 40° F. to about110° F., wherein at least a portion of the unreacted ethylene from thelight gas stream is absorbed by the absorption solvent system; andrecovering unreacted ethylene from the absorption solvent system toyield recovered ethylene.

Embodiment B. The process of embodiment A, wherein the absorptionsolvent system comprises copper chloride, aniline, andN-methylpyrrolidone.

Embodiment C. The process of embodiments A through B, wherein thecontacting the light gas stream with the absorption solvent systemoccurs at a temperature in a range of from about 40° F. to about 60° F.

Embodiment D. The process of embodiments A through C, wherein thecontacting the light gas stream with the absorption solvent systemoccurs at a temperature of about 50° F.

Embodiment E. The process of embodiments A through B, wherein thecontacting the light gas stream with the absorption solvent systemoccurs at a temperature in a range of from about 60° F. to about 90° F.

Embodiment F. The process of embodiments A through E, furthercomprising:

introducing a stripping gas into the absorption solvent system, whereinat least a portion of the stripping gas is absorbed by the absorptionsolvent system.

Embodiment G. The process of embodiment F, wherein the stripping gas isselected from the group consisting of nitrogen and isobutane.

Embodiment H. The process of embodiments A through G, wherein thecontacting the light gas stream with the absorption solvent systemcomprises bubbling the light gas stream through a packed bed in theabsorption solvent system.

Embodiment I. The process of embodiments A through H, wherein thecontacting the light gas stream with the absorption solvent systemcomprises pressurizing the light gas stream and the absorption solventsystem to a pressure in a range of from about 40 psig to about 60 psig.

Embodiment J. The process of embodiments A through I, wherein therecovering unreacted ethylene from the absorption solvent systemcomprises depressurizing the absorption solvent system having absorbedunreacted ethylene at a temperature in a range of from about 110° F. toabout 200° F.

Embodiment K. The process of embodiments A through J, wherein thedepressurizing the absorption solvent system occurs at a pressure in arange of from about 0 psig to about 10 psig.

Embodiment L. The process of embodiments A through K, wherein thedepressurizing the absorption solvent system having absorbed unreactedethylene occurs at a temperature in a range of from about 140° F. toabout 160° F.

Embodiment M. The process of embodiments A through K, wherein thedepressurizing the absorption solvent system having absorbed unreactedethylene occurs at a temperature in a range of from about 160° F. toabout 200° F.

Embodiment N. The process of embodiments A through M, furthercomprising:

removing at least a portion of elemental oxygen or oxygen-containingcompounds from the light gas stream before contacting the light gasstream with the absorption solvent system.

Embodiment O. A polyethylene production process, comprising:

contacting ethylene and a polymerization catalyst in a polymerizationreactor under suitable reaction conditions to yield a polymerizationproduct stream;

separating a light gas stream from the polymerization product stream,wherein the light gas stream comprises unreacted ethylene;

contacting the light gas stream with an absorption solvent system in anabsorption reactor at a temperature in a range of from about 40° F. toabout 110° F., wherein at least a portion of the unreacted ethylene fromthe light gas stream is absorbed by the absorption solvent system toyield a composition comprising a complex of the absorption solventsystem and unreacted ethylene;

removing unabsorbed gases of the light gas stream from contact with theabsorption solvent system;

recovering unreacted ethylene from the absorption solvent system; and

contacting the recovered ethylene and the polymerization catalyst.

Embodiment P. The process of embodiment O, further comprising:

introducing a stream comprising the composition comprising the complexof the absorption solvent system and unreacted ethylene into a solventregenerator at a temperature in a range of about 50° F. to about 200°F.;

recovering unreacted ethylene from the composition comprising thecomplex of the absorption solvent system and unreacted ethylene to yieldrecovered ethylene and a regenerated absorption solvent system;

introducing a stream comprising the recovered ethylene into thepolymerization reactor; and

introducing a stream comprising the regenerated absorption solventsystem into the absorption reactor.

Embodiment Q. The process of embodiments O through P, wherein theintroducing a stream comprising the composition comprising the complexof the absorption solvent system and unreacted ethylene into a solventregenerator occurs at a pressure in a range of about 0 psig to about 10psig.

Embodiment R. The process of embodiment O, wherein the recoveringunreacted ethylene from the absorption solvent system comprisesdepressurizing the absorption reactor to a pressure in a range of fromabout 0 psig to about 10 psig.

Embodiment S. The process of embodiments A through R, furthercomprising:

removing unabsorbed gases of the light gas stream from contact with theabsorption solvent system to form a waste gas stream.

Embodiments T. The process of embodiment S, further comprising:

processing the waste gas stream in a processing device, wherein theprocessing device comprises a cracker, catalytic cracker, scrubber,converter, treater, dehydrogenator, deoxygenator, flare or combinationsthereof.

Embodiment U. The process of embodiments 0 through T, wherein theabsorption solvent system comprises copper chloride, aniline, andN-methylpyrrolidone.

Embodiment V. The process of embodiments 0, R through U, wherein thecontacting the light gas stream with the absorption solvent system in anabsorption reactor comprises pressurizing the absorption reactor to apressure in a range of from about 40 psig to about 60 psig.

Embodiment W. The process of embodiments 0 through V, furthercomprising:

removing at least a portion of elemental oxygen or oxygen-containingcompounds from the light gas stream before introducing the light gasstream into the absorption reactor.

Embodiment X. A polyethylene production system, comprising:

a feed stream comprising ethylene, wherein the feed stream ischaracterized by introduction into a polymerization reactor;

a polymerization product stream, wherein the polymerization productstream is characterized by emission from the polymerization reactor andintroduction into a separator;

a light gas stream comprising unreacted ethylene, wherein the light gasstream is characterized by emission from the separator, the light gasstream having been separated from the polymerization product stream,wherein the light gas stream is characterized by introduction into anabsorption solvent system, wherein the absorption solvent system has atemperature in a range of from about 40° F. to about 110° F.;

an absorbent-ethylene conjugant, wherein the absorbent-ethyleneconjugant is characterized by formation within the absorption solventsystem by absorption of at least a portion of the unreacted ethylene bythe absorption solvent system; and

a waste gas stream comprising ethane, wherein the waste gas stream ischaracterized by emission from the absorption reactor, wherein the wastegas stream comprises components of the light gas stream that are notabsorbed by the absorption solvent system; and

a recovered unreacted ethylene stream, wherein the recovered unreactedethylene stream is characterized by emission from the absorption reactorand reintroduction into the polymerization reactor.

Embodiment Y. The system of embodiment X, wherein recovery of therecovered unreacted ethylene from the absorbent-ethylene conjugantoccurs via a pressure reduction from a pressure of the absorptionreactor to a pressure in a range of from about 0 psig to about 10 psig.

Embodiment Z. The system of embodiments X through Y, wherein recovery ofthe recovered unreacted ethylene from the absorbent-ethylene conjugantoccurs at a temperature in a range of about 110° F. to about 200° F.

Embodiment AA. The system of embodiments X through Z, wherein theabsorption solvent system comprises copper chloride, aniline, andN-methylpyrrolidone.

Embodiment AB. A polyethylene production system, comprising:

a polymerization reactor, wherein the polymerization reactor isconfigured to receive a feed stream comprising ethylene, and wherein thepolymerization reactor is configured to emit a polymerization productstream;

a separator, wherein the separator is configured to receive thepolymerization product stream and to emit a light gas stream comprisingunreacted ethylene, wherein the light gas stream has been separated fromthe polymerization product stream; and

an absorption reactor comprising an absorption solvent system, whereinthe absorption reactor is configured to receive the light gas stream, toabsorb at least a portion of the unreacted ethylene with the absorptionsolvent system at a temperature in a range of from about 40° F. to about110° F., and to emit a waste gas stream comprising components of thelight gas stream that are not absorbed by the absorption solvent system,and wherein the absorption reactor is further configured to emit arecovered unreacted ethylene stream, and wherein the polymerizationreactor is further configured to receive the recovered unreactedethylene stream.

Embodiment AC. The system of embodiment AB, wherein the recoveredunreacted ethylene is recovered from the absorption solvent system via apressure reduction from a pressure of the absorption reactor to apressure in a range of from about 0 psig to about 10 psig.

Embodiment AD. The system of embodiments AB through AC, wherein therecovered unreacted ethylene is recovered from the absorption solventsystem via a temperature increase from the absorption temperature to atemperature in a range of from about 110° F. to about 200° F.

Embodiment AE. The system of embodiments AB through AD, wherein theabsorption reactor comprises two or more packed-bed reactors, whereinthe recovered unreacted ethylene is recovered from the absorptionsolvent system via a pressure reduction of one of the two or morepacked-bed reactors while another of the packed bed reactors operates ata pressure in a range of from about 40 psig to about 60 psig.

Embodiment AF. The system of embodiments AB through AE, wherein theabsorption solvent system comprises copper chloride, aniline, andN-methylpyrrolidone.

Embodiment AG. The system of embodiments AB through AF, furthercomprising a second absorption reactor, wherein the absorption reactorsare configured to absorb ethylene in a liquid solvent through pressureswing absorption.

Embodiment AH. A polyethylene production system, comprising:

a polymerization reactor, wherein the polymerization reactor isconfigured to receive a feed stream comprising ethylene, and wherein thepolymerization reactor is configured to emit a polymerization productstream;

a separator, wherein the separator is configured to receive thepolymerization product stream and to emit a light gas stream comprisingunreacted ethylene, wherein the light gas stream has been separated fromthe polymerization product stream;

an absorption reactor comprising an absorption solvent system, whereinthe absorption reactor is configured to receive the light gas stream, toabsorb at least a portion of the unreacted ethylene with the absorptionsolvent system at a temperature in a range of from about 40° F. to about110° F. and to emit a waste gas stream comprising components of thelight gas stream that are not absorbed by the absorption solvent system,wherein the absorption reactor is further configured to emit a complexedstream comprising ethylene absorbed in the absorbent solvent system; and

a solvent regenerator to regenerate the absorption solvent system, andto emit a recovered unreacted ethylene stream, wherein thepolymerization reactor is further configured to receive the recoveredunreacted ethylene stream.

Embodiment AI. The system of embodiment AH, wherein the solventregenerator is configured to operate at a pressure in a range of fromabout 0 psig to about 10 psig.

Embodiment AJ. The system of embodiments AH through AI, wherein thesolvent regenerator is configured to operate at a temperature in a rangeof from about 110° F. to about 200° F.

Embodiment AK. The system of embodiments X through AJ, furthercomprising a processing device configured to receive the waste gasstream.

Embodiment AL. The system of embodiment AK, wherein the processingdevice comprises a cracker, catalytic cracker, scrubber, converter,treater, dehydrogenator, deoxygenator, flare or combinations thereof.

EXAMPLES

The disclosure having been generally described, the following examplesare given as particular embodiments of the disclosure and to demonstratethe practice and advantages thereof. It is understood that theseexamples are given by way of illustration and is not intended to limitthe specification or the claims in any manner.

A computerized commercial process simulator was employed to generate anoutput from a model in accordance with the systems and/or processesdisclosed herein. The model employed is illustrated at FIG. 9, whichshows an embodiment of a system 900, as disclosed herein, and shall beused to describe the examples below. In the embodiment shown in FIG. 9,a light gas stream 18, which was separated from a polymerization productstream of a polyethylene reactor, feeds to an absorption reactor 116.The total molar and mass flows and component molar and mass flows of thelight gas stream 18 are shown in Table 1 below:

TABLE 1 Total Molar Flow 52.9 Total Mass Flow (lb/hr) 1127 (lbmol/hr)Component Molar Flow Component Mass Flow (lbmol/hr) (lb/hr) Hydrogen15.4 Hydrogen 31 Nitrogen 4.9 Nitrogen 137 Ethylene 26 Ethylene 729Ethane 5.6 Ethane 169 Isobutane 1.1 Isobutane 62 Component MolarComponent Mass Fraction Fraction Hydrogen 0.291 Hydrogen 0.028 Nitrogen0.092 Nitrogen 0.121 Ethylene 0.491 Ethylene 0.646 Ethane 0.106 Ethane0.150 Isobutane 0.020 Isobutane 0.055

Unreacted ethylene that enters the absorption reactor 116 is absorbed inthe absorption solvent system within the absorption reactor 116.Absorbed unreacted ethylene flows, as complexed stream 28, to a firstregenerator 120. In stream 28, the absorbed ethylene is heated by heatexchanger REG1HEAT before entering the first regenerator 120. Ethylenedesorbs from the solvent from the absorption solvent system in firstregenerator 120 and flows through stream 29 to a second regenerator 122.Stream 29 may be cooled with heat exchanger REG2COOL before entering thesecond regenerator 122. Ethylene is recovered in stream 20. Absorptionsolvent in streams 32 and 34 combine in heat exchanger FEEDCOOL torecycle to the absorption reactor 116 in stream 30.

Table 2 shows operating conditions for examples 1-44 of ethylenerecovery using the system 900 of FIG. 9. For the examples shown in Table2, the absorption solvent system comprises a copper chloride, aniline,and NMP system, as disclosed herein, and composition of the purifiedproduct is based on 90% ethylene recovery. The composition of thepurified product recovered in FIG. 9 comprises ethylene, ethane,nitrogen, hydrogen, and isobutane. The wt % of each of these componentsin the purified product is shown in Table 2. The purified productcompositions shown in Table are compositions of stream 20 in FIG. 9.Select examples from Table 2 are discussed in detail below.

Example 3

In Example 3 of Table 2, the absorption reactor 116 in FIG. 9 operatesat a temperature of 15° F., with a lean solvent temperature of 14° F.and pressure of 40 psig. The first regenerator 120 operates at atemperature of 150° F. and pressure of 0 psig. The second regenerator122 operates at a temperature of 50° F. and pressure of 0 psig. Underthese conditions, system 900 recovers 90% of the ethylene and thesolvent circulation flow rate to 344,776 lb/hr and the amount ofethylene in the purified product to 64.5%.

Example 4

In Example 4 of Table 2, the operating conditions are the same asExample 3, except the first regenerator 120 operates at a temperature of200° F. and pressure of 0 psig. Under these conditions, system 900recovers 90% of ethylene for a solvent circulation flow rate of 143,736lb/hr, and the purified product contains 77.5% ethylene.

Example 7

In Example 7 of Table 2, the absorption reactor 116 in FIG. 9 operatesat a temperature of 53° F., with a lean solvent temperature of 50° F.Absorption reactor 116 also operates at a pressure of 40 psig. The firstregenerator 120 operates at a temperature of 150° F. and a pressure of 0psig. The second regenerator 122 operates at a temperature of 50° F. anda pressure of 0 psig. Under these conditions, system 900 recovers 90% ofthe ethylene for a solvent circulation flow rate of 53,920 lb/hr. Thepurified product composition for Example 7 is shown in Table 2.

When comparing Example 7 with the Examples 3 and 4, the solventcirculation flow rate of 53,920 lb/hr in Example 7 is less than the flowrates of 143,736 lb/hr and 344,776 lb/hr in the Examples 3 and 4. Thus,Example 7 shows the solvent circulation flow rate required to absorbethylene in a copper chloride aniline NMP absorption solvent system ismuch less for an absorption temperature of 53° F. than for an absorptiontemperature of 15° F. because of the unexpected drop in solubility forethylene in the absorption solvent system for temperatures below about50° F.

Example 8

In Example 8 of Table 2, the absorption reactor 116 in FIG. 9 operatesat a temperature of 55° F., with a lean solvent temperature of 50° F.Absorption reactor 116 also operates at a pressure of 40 psig. The firstregenerator 120 operates at a temperature of 200° F. and a pressure of 0psig. The second regenerator 122 operates at a temperature of 50° F. anda pressure of 0 psig. Under these conditions, system 800 recovers 90% ofthe ethylene for a solvent circulation flow rate of 47,785 lb/hr. Thepurified product composition for Example 8 is shown in Table 2.

Example 8 confirms the results shown in Example 7 that lower solventcirculation flow rates are required when the absorption reactor 116operates at a temperature of 55° F. instead of temperatures below 50° F.Example 2 additionally shows varying the temperature of the regenerators120 from 150° F. to 200° F. does not affect the solvent circulation flowrate to a significant degree.

Example 19

In Example 19 of Table 2, the absorption reactor 116 in FIG. 9 operatesat a temperature of 53° F., with a lean solvent temperature of 50° F.Absorption reactor 116 also operates at a pressure of 40 psig. The firstregenerator 120 operates at a temperature of 200° F. and a pressure of10 psig. The second regenerator 122 operates at a temperature of 50° F.and a pressure of 10 psig. Under these conditions, system 900 recovers90% of the ethylene for a solvent circulation flow rate of 59,272 lb/hr.The purified product composition is shown in Table 2.

Example 19 confirms the lower solvent circulation rates discussed inExamples 7 and 8 when compared to Examples 3 and 4. Example 19 alsoshows varying the pressure of the first and second regenerators 120 and122 between 0 psig and 10 psig does not significantly alter results.Operation of the regenerators 120 and 122 at 0 psig may provide a lowersolvent circulation rate as well as enhanced product purity, andoperation of the regenerators 120 and 122 at 10 psig may provide a saferdesign because a positive pressure in the regenerators 120 and 122reduces a chance of air and water infiltration via leaks in the systemand process, which may react with copper chloride in the absorptionsolvent system and inhibit performance.

Example 28

In Example 28 of Table 2, the absorption reactor 116 in FIG. 9 operatesat 52° F., with a lean solvent temperature of 50° F. Absorption reactor116 also operates at a pressure of 60 psig. The first regenerator 120operates at a temperature of 100° F. and a pressure of 0 psig. Thesecond regenerator 122 operates at a temperature of 50° F. and apressure of 0 psig. Under these conditions, system 900 recovers 90% ofthe ethylene for a solvent circulation flow rate of 58,613 lb/hr. Thepurified product composition is shown in Table 2.

Under the conditions in Example 28, the solvent circulation flow rate isless than that of the Examples 3 and 4, and the amount of ethylene inthe purified product is significantly higher.

Example 29

In Example 29 of FIG. 2, the absorption reactor 116 in FIG. 9 operatesat 55° F., with a lean solvent temperature of 50° F. Absorption reactor116 also operates at a pressure of 60 psig. The first regenerator 120operates at a temperature of 150° F. and a pressure of 0 psig. Thesecond regenerator 122 operates at a temperature of 50° F. and apressure of 0 psig. Under these conditions, system 900 recovers 90% ofthe ethylene for a circulation flow rate of solvent of 51,106 lb/hr. Thepurified product composition is shown in Table 2.

Under the conditions in Example 29, the solvent circulation flow rate isless than that of the Examples 3 and 4, and the amount of ethylene inthe purified product is significantly higher.

Example 30

In Example 30 of Table 2, the absorption reactor 116 in FIG. 9 operatesat 56° F., with a lean solvent temperature of 50° F. Absorption reactor116 also operates at a pressure of 60 psig. The first regenerator 120operates at a temperature of 200° F. and a pressure of 0 psig. Thesecond regenerator 122 operates at a temperature of 50° F. and apressure of 0 psig. Under these conditions, system 900 recovers 90% ofthe ethylene for a circulation flow rate of solvent of 46,744 lb/hr. Thepurified product composition is shown in Table 2.

Under the conditions in Example 30, the solvent circulation flow rate isless than that of the Examples 3 and 4, and the amount of ethylene inthe purified product is significantly higher.

Example 33

In Example 33 of Table 2, the absorption reactor 116 in FIG. 9 operatesat a temperature of 102° F., with a lean solvent temperature of 100° F.Absorption reactor 116 also operates at a pressure of 60 psig. The firstregenerator 120 operates at a temperature of 200° F. and a pressure of 0psig. The second regenerator 122 operates at a temperature of 50° F. anda pressure of 0 psig. Under these conditions, system 900 recovers 90% ofthe ethylene for a solvent circulation flow rate of 63,435 lb/hr. Thepurified product composition for Example 33 is shown in Table 2.

Under the conditions in Example 33, the solvent circulation flow rate isless than that of the Examples 3 and 4, and the amount of ethylene inthe purified product is significantly higher. Moreover, Example 33 showthat operation of the absorption reactor 116 at temperatures higher thanthe temperatures of maximum solubility shown in FIG. 7, for example, at102° F. as shown in Example 33, may still prove economically feasiblebecause, for example, solvent circulation flow rates remain low comparedwith conditions of Examples 3 and 4.

Example 40

In Example 40 of Table 2, the absorption reactor 116 in FIG. 9 operatesat a temperature of 52° F., with a lean solvent temperature of 50° F.Absorption reactor 116 also operates at a pressure of 60 psig. The firstregenerator 120 operates at a temperature of 150° F. and a pressure of10 psig. The second regenerator 122 operates at a temperature of 50° F.and a pressure of 10 psig. Under these conditions, system 900 recovers90% of the ethylene for a solvent circulation flow rate of 57,441 lb/hr.The purified product composition for Example 40 is shown in Table 2.

Under the conditions in Example 40, the solvent circulation flow rate isless than that of the Examples 3 and 4, and the amount of ethylene inthe purified product is significantly higher.

Example 41

In Example 41 of Table 2, the absorption reactor 116 in FIG. 9 operatesat 55° F., with a lean solvent temperature of 50° F. Absorption reactor116 also operates at a pressure of 60 psig. The first regenerator 120operates at a temperature of 200° F. and a pressure of 10 psig. Thesecond regenerator 122 operates at a temperature of 50° F. and apressure of 10 psig. Under these conditions, system 900 recovers 90% ofthe ethylene for a circulation flow rate of solvent of 51,482 lb/hr. Thepurified product composition is shown in Table 2.

Under the conditions in Example 41, the solvent circulation flow rate isless than that of the Examples 3 and 4, and the amount of ethylene inthe purified product is significantly higher.

Example Simulation

A computerized commercial process simulator was employed to generate anoutput from a model in accordance with the systems and/or processesdisclosed herein. The model employed is illustrated at FIG. 10, whereina gaseous stream, designated VAP FEED (e.g., the light gas streamdisclosed herein) feeds to absorption reactor ASORB1. The outputgenerated by the commercial process simulator is a material balance anda heat balance, shown in Table 3. The names designating the variousstreams listed in Table 3 correspond to streams illustrated in FIG. 10.In FIG. 10, ASORB1 is the absorption reactor, which is shown as a fourstage absorber operating at 90° F.

TABLE 2 Ab- Flow sorber rate of Lean top REG1 REG2 Ab- REG1 REG2 circu-Ex- Solvent temper- temper- temper- sorber temper- temper- lation am-Temp. ature ature ature pressure ature ature Ethylene solvent EthyleneEthane Nitrogen Hydrogen Isobutane ple (° F.) (° F.) (° F.) (° F.)(psig) (psig) (psig) Recovery (lb/hr) (wt %) (wt %) (wt %) (wt %) (wt %)1 14 15 50 50 40 0 0 90% 1704044 48.9% 11.6% 10.0% 27.2% 2.2% 2 14 15100 50 40 0 0 90% 731337 57.7% 13.0% 11.1% 18.9% 2.3% 3 14 15 150 50 400 0 90% 344776 64.5% 15.2% 8.5% 9.5% 2.2% 4 14 15 200 50 40 0 0 90%143736 77.5% 16.3% 2.1% 3.3% 0.8% 5 50 50 50 50 40 0 0 90% 672565 62.1%13.3% 7.0% 15.1% 2.5% 6 50 51 100 50 40 0 0 90% 158735 81.9% 11.2% 1.8%4.1% 1.0% 7 50 53 150 50 40 0 0 90% 53920 95.9% 2.3% 0.5% 1.1% 0.3% 8 5055 200 50 40 0 0 90% 47785 96.5% 1.9% 0.4% 1.0% 0.3% 9 100 100 100 50 400 0 90% 921807 62.1% 13.0% 7.1% 15.3% 2.5% 10 100 100 150 50 40 0 0 90%343211 78.4% 9.5% 3.2% 7.1% 1.9% 11 100 101 200 50 40 0 0 90% 8840395.6% 1.9% 0.7% 1.4% 0.4% 12 14 14 50 50 40 10 10 N/A 13 14 15 100 50 4010 10 90% 1321719 50.3% 12.0% 10.2% 25.3% 2.2% 14 14 14 150 50 40 10 1090% 685442 56.2% 13.3% 10.6% 17.7% 2.3% 15 14 15 200 50 40 10 10 90%420362 64.1% 14.8% 7.1% 11.7% 2.4% 16 50 50 50 50 40 10 10 90% 136765754.8% 11.8% 9.0% 22.2% 2.2% 17 50 50 100 50 40 10 10 90% 463945 66.9%14.6% 5.1% 11.1% 2.3% 18 50 51 150 50 40 10 10 90% 121635 86.6% 8.1%1.3% 3.1% 0.8% 19 50 53 200 50 40 10 10 90% 59272 95.6% 2.5% 0.5% 1.2%0.3% 20 100 100 100 50 40 10 10 90% 1828349 54.8% 11.6% 9.0% 22.3% 2.2%21 100 100 150 50 40 10 10 90% 880270 64.5% 12.7% 5.7% 14.7% 2.4% 22 100100 200 50 40 10 10 90% 415884 77.5% 9.6% 2.3% 8.4% 2.1% 23 14 15 50 5060 0 0 90% 858069 50.7% 12.0% 10.4% 24.7% 2.2% 24 14 15 100 50 60 0 090% 384021 58.5% 13.9% 11.4% 13.7% 2.5% 25 14 15 150 50 60 0 0 90%159379 71.6% 16.9% 4.5% 5.6% 1.4% 26 14 16 200 50 60 0 0 90% 93956 82.2%12.7% 1.7% 2.8% 0.7% 27 50 50 50 50 60 0 0 90% 296859 68.5% 14.6% 4.6%9.8% 2.5% 28 50 52 100 50 60 0 0 90% 58613 93.9% 3.4% 0.7% 1.6% 0.4% 2950 55 150 50 60 0 0 90% 51106 94.7% 2.9% 0.6% 1.4% 0.4% 30 50 56 200 5060 0 0 90% 46744 95.3% 2.6% 0.5% 1.3% 0.3% 31 100 100 100 50 60 0 0 90%428830 68.5% 13.3% 5.0% 10.6% 2.6% 32 100 100 150 50 60 0 0 90% 11116190.5% 4.1% 1.5% 3.0% 0.9% 33 100 102 200 50 60 0 0 90% 63435 95.7% 1.8%0.7% 1.4% 0.4% 34 14 14 50 50 60 10 10 N/A 35 14 15 100 50 60 10 10 90%693610 52.5% 12.5% 10.6% 22.1% 2.3% 36 14 15 150 50 60 10 10 90% 34610160.5% 14.3% 10.5% 12.3% 2.4% 37 14 15 200 50 60 10 10 90% 181196 71.0%16.3% 4.4% 6.7% 1.6% 38 50 50 50 50 60 10 10 90% 669442 58.7% 12.6% 8.2%18.2% 2.3% 39 50 51 100 50 60 10 10 90% 179196 75.0% 15.2% 2.6% 5.8%1.4% 40 50 52 150 50 60 10 10 90% 57441 94.1% 3.3% 0.7% 1.6% 0.4% 41 5055 200 50 60 10 10 90% 51482 94.8% 2.9% 0.5% 1.4% 0.4% 42 100 100 100 5060 10 10 90% 896707 58.7% 12.4% 8.3% 18.3% 2.4% 43 100 100 150 50 60 1010 90% 378813 71.8% 12.1% 4.1% 9.6% 2.4% 44 100 100 200 50 60 10 10 90%130215 89.1% 4.8% 14.3% 3.7% 1.1%

TABLE 3 L1CUCLL L2CUCLR L3CUCLR2 L4CUCLR3 L5CUCLL Substream: MIXED MoleFlow lb mol/hr C2═ 1.949416 41.85801 41.85801 41.85801 1.949413 C20.9764562 5.916248 5.916248 5.916248 0.9764532 N2 1.15E−03 0.17116790.1711679 0.1711679 1.15E−03 IC4 0.8615088 3.112527 3.112527 3.1125270.8615092 CUCL 131.4402 131.4402 131.4402 131.4402 131.4402 ANILINE580.5749 580.5749 580.5749 580.5749 580.5748 NMP 789.7864 789.7864789.7864 789.7864 789.7864 Mole Frac C2═ 1.29E−03 0.0269554 0.02695540.0269554 1.29E−03 C2 6.49E−04 3.81E−03 3.81E−03 3.81E−03 6.49E−04 N27.64E−07 1.10E−04 1.10E−04 1.10E−04 7.64E−07 IC4 5.72E−04 2.00E−032.00E−03 2.00E−03 5.72E−04 CUCL 0.0873014 0.0846439 0.0846439 0.08464390.0873014 ANILINE 0.3856129 0.3738747 0.3738747 0.3738747 0.3856128 NMP0.5245694 0.5086013 0.5086013 0.5086013 0.5245694 Mass Flow lb/hr C2═54.68846 1174.274 1174.274 1174.274 54.68837 C2 29.36169 177.8994177.8994 177.8994 29.3616 N2 0.0322059 4.795009 4.795009 4.7950090.0322058 IC4 50.07382 180.9106 180.9106 180.9106 50.07384 CUCL 13012.4113012.41 13012.41 13012.41 13012.41 ANILINE 54067.97 54067.97 54067.9754067.97 54067.96 NMP 78293.58 78293.58 78293.58 78293.58 78293.58 MassFrac C2═ 3.76E−04 7.99E−03 7.99E−03 7.99E−03 3.76E−04 C2 2.02E−041.21E−03 1.21E−03 1.21E−03 2.02E−04 N2 2.21E−07 3.26E−05 3.26E−053.26E−05 2.21E−07 IC4 3.44E−04 1.23E−03 1.23E−03 1.23E−03 3.44E−04 CUCL0.0894273 0.0885729 0.0885729 0.0885729 0.0894273 ANILINE 0.37158040.36803 0.36803 0.36803 0.3715804 NMP 0.5380702 0.532929 0.5329290.532929 0.5380702 Total Flow 1505.59 1552.86 1552.86 1552.86 1505.59 lbmol/hr Total Flow 145508 1.47E+05 1.47E+05 1.47E+05 1.46E+05 lb/hr TotalFlow 2000 2063.515 9563.191 13833 2058.304 cuft/hr Temperature F. 90105.0961 95.53801 140 158 Pressure psia 117.6959 114.6959 25 25 25 VaporFrac 0 0 0.020591 0.0297334 0 Liquid Frac 1 1 0.9794089 0.9702665 1Solid Frac 0 0 0 0 0 Enthalpy −60439.71 −58273.13 −58273.13 −56229.58−57622.43 Btu/lb mol Enthalpy −625.377 −615.9475 −615.9475 −594.3472−596.2263 Btu/lb Enthalpy −9.10E+07 −9.05E+07 −9.05E+07 −8.73E+07−8.68E+07 Btu/hr Entropy −112.3696 −109.6524 −109.5691 −106.0242−107.4881 Btu/lb mol-R Entropy −1.162701 −1.159027 −1.158146 −1.120676−1.112192 Btu/lb-R Density 0.75276 0.7525312 0.1623788 0.11225760.7314713 lb mol/cuft Density 72.75067 71.19494 15.36222 10.6203970.69322 lb/cuft Average MW 96.64524 94.6073 94.6073 94.6073 96.64524Liq Vol 60 F. 2474.029 2538.765 2538.765 2538.765 2474.029 cuft/hrL6CUCLL LKO1 LKO2 LKO3 V1 Substream: MIXED Mole Flow lb mol/hr C2═1.949413 2.02E−04 4.41E−03 9.89E−04 3.172776 C2 0.9764532 6.17E−048.14E−04 2.10E−04 5.654325 N2 1.15E−03 8.35E−06 8.99E−07 6.78E−087.187729 IC4 0.8615092 2.14E−04 2.23E−03 1.08E−03 0.1670439 CUCL131.4402 1.50E−13 2.85E−13 0 1.50E−13 ANILINE 580.5748 2.47E−030.2059512 0.0219362 2.48E−03 NMP 789.7864 2.38E−03 0.1961199 9.42E−032.38E−03 Mole Frac C2═ 1.29E−03 0.0343637 0.0107758 0.0294004 0.1960108C2 6.49E−04 0.1047838 1.99E−03 6.25E−03 0.3493185 N2 7.64E−07 1.42E−032.19E−06 2.02E−06 0.4440506 IC4 5.72E−04 0.0362971 5.44E−03 0.0321520.0103198 CUCL 0.0873014 2.54E−11 6.97E−13 0 9.24E−15 ANILINE 0.38561280.4198489 0.5029009 0.6521121 1.53E−04 NMP 0.5245694 0.4032882 0.47889450.2800845 1.47E−04 Mass Flow lb/hr C2═ 54.68837 5.68E−03 0.12380090.027745 89.00829 C2 29.3616 0.0185606 0.0244775 6.32E−03 170.0235 N20.0322058 2.34E−04 2.52E−05 1.90E−06 201.3533 IC4 50.07384 0.01242770.129461 0.0628636 9.709158 CUCL 13012.41 1.48E−11 2.83E−11 0 1.48E−11ANILINE 54067.96 0.2303272 19.17989 2.042886 0.2311832 NMP 78293.580.2355062 19.44187 0.9339974 0.2358215 Mass Frac C2═ 3.76E−04 0.01129593.18E−03 9.03E−03 0.1891534 C2 2.02E−04 0.0369193 6.29E−04 2.06E−030.3613207 N2 2.21E−07 4.66E−04 6.47E−07 6.18E−07 0.4279003 IC4 3.44E−040.0247203 3.33E−03 0.0204513 0.0206331 CUCL 0.0894273 2.95E−11 7.26E−130 3.15E−14 ANILINE 0.3715804 0.4581486 0.4930622 0.6646093 4.91E−04 NMP0.5380702 0.4684502 0.4997972 0.3038561 5.01E−04 Total Flow 1505.595.89E−03 0.4095263 0.0336387 16.18674 lb mol/hr Total Flow 1.46E+050.5027346 38.89952 3.073815 470.5613 lb/hr Total Flow 2058.521 8.16E−030.6204605 0.04765 825.9148 cuft/hr Temperature F. 158.2431 −20 90 −2096.94405 Pressure psia 118.6959 114.6959 24.9 24.8 114.6959 Vapor Frac 00 0 0 1 Liquid Frac 1 1 1 1 0 Solid Frac 0 0 0 0 0 Enthalpy −57585.8−49592.05 −47471.61 −28177.63 −8659.402 Btu/lb mol Enthalpy −595.8472−581.0902 −499.7715 −308.3662 −297.8729 Btu/lb Enthalpy −8.67E+07−292.1342 −19440.87 −947.8608 −1.40E+05 Btu/hr Entropy −107.4788−111.4813 −112.727 −110.4079 −19.64671 Btu/lb mol-R Entropy −1.112096−1.306271 −1.186767 −1.208266 −0.6758228 Btu/lb-R Density 0.7313940.7221323 0.6600361 0.7059546 0.0195985 lb mol/cuft Density 70.6857561.62902 62.6946 64.50811 0.5697456 lb/cuft Average MW 96.64524 85.3431194.98663 91.37714 29.0708 Liq Vol 60 F. 2474.029 8.78E−03 0.61656120.0501975 18.42872 cuft/hr V1FLARE V2 V3 VAP-REC VAPFEED Substream:MIXED Mole Flow lb mol/hr C2═ 3.172573 39.91302 39.9096 39.9086143.08116 C2 5.653708 4.940621 4.940017 4.939807 10.5935 N2 7.1877210.1700194 0.1700186 0.1700185 7.357739 IC4 0.1668301 2.253242 2.2520962.251014 2.417848 CUCL 4.78E−22 2.85E−13 2.86E−24 0 0 ANILINE 9.19E−060.20608 0.022065 1.29E−04 0 NMP 3.17E−06 0.1961404 9.44E−03 2.06E−05 0Mole Frac C2═ 0.1960697 0.8371173 0.843697 0.8442764 0.6789755 C20.3494075 0.1036223 0.104433 0.1045028 0.1669576 N2 0.4442117 3.57E−033.59E−03 3.60E−03 0.1159608 IC4 0.0103103 0.0472584 0.0476097 0.04762070.0381062 CUCL 2.95E−23 5.99E−15 6.04E−26 0 0 ANILINE 5.68E−07 4.32E−034.66E−04 2.73E−06 0 NMP 1.96E−07 4.11E−03 2.00E−04 4.36E−07 0 Mass Flowlb/hr C2═ 89.00261 1119.71 1119.614 1119.587 1208.589 C2 170.005148.5627 148.5445 148.5382 318.5427 N2 201.3531 4.762835 4.7628124.76281 206.1159 IC4 9.69673 130.9661 130.8995 130.8366 140.5336 CUCL4.73E−20 2.83E−11 2.83E−22 0 0 ANILINE 8.56E−04 19.19188 2.0548830.0120247 0 NMP 3.14E−04 19.4439 0.9360284 2.04E−03 0 Mass Frac C2═0.1893437 0.7761549 0.7958521 0.797575 0.645 C2 0.3616676 0.10297990.1055895 0.1058162 0.17 N2 0.4283574 3.30E−03 3.39E−03 3.39E−03 0.11IC4 0.0206287 0.0907823 0.0930468 0.0932058 0.075 CUCL 1.01E−22 1.96E−142.01E−25 0 0 ANILINE 1.82E−06 0.0133033 1.46E−03 8.57E−06 0 NMP 6.69E−070.013478 6.65E−04 1.46E−06 0 Total Flow 16.18085 47.67913 47.3032447.2696 63.45025 lb mol/hr Total Flow 470.0586 1442.638 1406.8121403.738 1873.781 lb/hr Total Flow 634.7071 12547.34 11089.96 8812.5441155.656 cuft/hr Temperature F. −20 158 90 −20 0 Pressure psia 114.695925 24.9 24.8 226.6959 Vapor Frac 1 1 1 1 0.9823996 Liquid Frac 0 0 0 00.0176004 Solid Frac 0 0 0 0 0 Enthalpy −9795.256 13137.72 12629.8811470.01 5793.013 Btu/lb mol Enthalpy −337.1825 434.201 424.6725 386.242196.1639 Btu/lb Enthalpy −1.59E+05 6.26E+05 5.97E+05 5.42E+05 3.68E+05Btu/hr Entropy −21.92954 −18.274 −19.22263 −21.55552 −25.0739 Btu/lbmol-R Entropy −0.7548814 −0.603955 −0.6463497 −0.7258623 −0.8490563Btu/lb-R Density 0.0254934 3.80E−03 4.27E−03 5.36E−03 0.0549041 lbmol/cuft Density 0.7405913 0.1149756 0.1268545 0.1592887 1.6214 lb/cuftAverage MW 29.05031 30.25722 29.74029 29.69643 29.5315 Liq Vol 60 F.18.41994 65.35257 64.78621 64.73601 83.15566 cuft/hr

At least one embodiment is disclosed and variations, combinations,and/or modifications of the embodiment(s) and/or features of theembodiment(s) made by a person having ordinary skill in the art arewithin the scope of the disclosure. Alternative embodiments that resultfrom combining, integrating, and/or omitting features of theembodiment(s) are also within the scope of the disclosure. Wherenumerical ranges or limitations are expressly stated, such expressranges or limitations should be understood to include iterative rangesor limitations of like magnitude falling within the expressly statedranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4,etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example,whenever a numerical range with a lower limit, R₁, and an upper limit,R_(u), is disclosed, any number falling within the range is specificallydisclosed. In particular, the following numbers within the range arespecifically disclosed: R=R₁+k*(R_(u)−R₁), wherein k is a variableranging from 1 percent to 100 percent with a 1 percent increment, i.e.,k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . 50percent, 51 percent, 52 percent . . . 95 percent, 96 percent, 97percent, 98 percent, 99 percent, or 100 percent. Moreover, any numericalrange defined by two R numbers as defined in the above is alsospecifically disclosed. Use of the term “optionally” with respect to anyelement of a claim means that the element is required, or alternatively,the element is not required, both alternatives being within the scope ofthe claim. Use of broader terms such as comprises, includes, and havingshould be understood to provide support for narrower terms such asconsisting of, consisting essentially of, and comprised substantiallyof. Accordingly, the scope of protection is not limited by thedescription set out above but is defined by the claims that follow, thatscope including all equivalents of the subject matter of the claims.Each and every claim is incorporated as further disclosure into thespecification and the claims are embodiment(s) of the disclosedinventive subject matter. The discussion of a reference in thedisclosure is not an admission that it is prior art, especially anyreference that has a publication date after the priority date of thisapplication. The disclosure of all patents, patent applications, andpublications cited in the disclosure are hereby incorporated byreference, to the extent that they provide exemplary, procedural orother details supplementary to the disclosure.

We claim:
 1. A process for the recovery of ethylene from apolymerization product stream of a polyethylene production system, theprocess comprising: separating a light gas stream from thepolymerization product stream, wherein the light gas stream comprisesethane and unreacted ethylene; contacting the light gas stream with anabsorption solvent system, wherein the contacting the light gas streamwith the absorption solvent system occurs at a temperature in a range offrom about 40° F. to about 60° F., wherein at least a portion of theunreacted ethylene from the light gas stream is absorbed by theabsorption solvent system; and recovering unreacted ethylene from theabsorption solvent system to yield recovered ethylene.
 2. The process ofclaim 1, wherein the absorption solvent system comprises copperchloride, aniline, and N-methylpyrrolidone.
 3. The process of claim 1,wherein the contacting the light gas stream with the absorption solventsystem occurs at a temperature in a range from about 45° F. to about 55°F.
 4. The process of claim 1, wherein the contacting the light gasstream with the absorption solvent system comprises bubbling the lightgas stream through a packed bed in the absorption solvent system.
 5. Theprocess of claim 1, wherein the contacting the light gas stream with theabsorption solvent system comprises pressurizing the light gas streamand the absorption solvent system to a pressure in a range of from about40 psig to about 60 psig.
 6. The process of claim 1, wherein therecovering unreacted ethylene from the absorption solvent systemcomprises depressurizing the absorption solvent system having absorbedunreacted ethylene at a temperature in a range of from about 110° F. toabout 200° F.
 7. The process of claim 6, wherein the depressurizing theabsorption solvent system occurs at a pressure in a range of from about0 psig to about 10 psig.
 8. The process of claim 6, wherein thedepressurizing the absorption solvent system having absorbed unreactedethylene occurs at a temperature in a range of from about 140° F. toabout 160° F.
 9. The process of claim 6, wherein the depressurizing theabsorption solvent system having absorbed unreacted ethylene occurs at atemperature in a range of from about 160° F. to about 200° F.
 10. Theprocess of claim 1, further comprising: removing at least a portion ofelemental oxygen or oxygen-containing compounds from the light gasstream before contacting the light gas stream with the absorptionsolvent system.
 11. A polyethylene production process, comprising:contacting ethylene and a polymerization catalyst in a polymerizationreactor under suitable reaction conditions to yield a polymerizationproduct stream; separating a light gas stream from the polymerizationproduct stream, wherein the light gas stream comprises unreactedethylene; contacting the light gas stream with an absorption solventsystem in an absorption reactor at a temperature in a range of fromabout 40° F. to about 60° F., wherein at least a portion of theunreacted ethylene from the light gas stream is absorbed by theabsorption solvent system to yield a composition comprising a complex ofthe absorption solvent system and unreacted ethylene; removingunabsorbed gases of the light gas stream from contact with theabsorption solvent system; recovering unreacted ethylene from theabsorption solvent system; and contacting the recovered ethylene and thepolymerization catalyst.
 12. The process of claim 11, furthercomprising: introducing a stream comprising the composition comprisingthe complex of the absorption solvent system and unreacted ethylene intoa solvent regenerator at a temperature in a range of about 50° F. toabout 200° F.; recovering unreacted ethylene from the compositioncomprising the complex of the absorption solvent system and unreactedethylene to yield recovered ethylene and a regenerated absorptionsolvent system; introducing a stream comprising the recovered ethyleneinto the polymerization reactor; and introducing a stream comprising theregenerated absorption solvent system into the absorption reactor. 13.The process of claim 12, wherein the introducing a stream comprising thecomposition comprising the complex of the absorption solvent system andunreacted ethylene into a solvent regenerator occurs at a pressure in arange of about 0 psig to about 10 psig.
 14. The process of claim 11,wherein the recovering unreacted ethylene from the absorption solventsystem comprises depressurizing the absorption reactor to a pressure ina range of from about 0 psig to about 10 psig.
 15. The process of claim11, further comprising: removing unabsorbed gases of the light gasstream from contact with the absorption solvent system to form a wastegas stream.
 16. The process of claim 11, wherein the absorption solventsystem comprises copper chloride, aniline, and N-methylpyrrolidone. 17.The process of claim 11, wherein the contacting the light gas streamwith the absorption solvent system in an absorption reactor comprisespressurizing the absorption reactor to a pressure in a range of fromabout 40 psig to about 60 psig.
 18. The process of claim 11, furthercomprising: removing at least a portion of elemental oxygen oroxygen-containing compounds from the light gas stream before introducingthe light gas stream into the absorption reactor.
 19. A polyethyleneproduction system, comprising: a feed stream comprising ethylene,wherein the feed stream is characterized by introduction into apolymerization reactor; a polymerization product stream, wherein thepolymerization product stream is characterized by emission from thepolymerization reactor and introduction into a separator; a light gasstream comprising unreacted ethylene, wherein the light gas stream ischaracterized by emission from the separator, the light gas streamhaving been separated from the polymerization product stream, whereinthe light gas stream is characterized by introduction into an absorptionsolvent system, wherein the absorption solvent system has a temperaturein a range of from about 40° F. to about 60° F.; an absorbent-ethyleneconjugant, wherein the absorbent-ethylene conjugant is characterized byformation within the absorption solvent system by absorption of at leasta portion of the unreacted ethylene by the absorption solvent system;and a waste gas stream comprising ethane, wherein the waste gas streamis characterized by emission from the absorption reactor, wherein thewaste gas stream comprises components of the light gas stream that arenot absorbed by the absorption solvent system; and a recovered unreactedethylene stream, wherein the recovered unreacted ethylene stream ischaracterized by emission from the absorption reactor and reintroductioninto the polymerization reactor.
 20. The system of claim 19, whereinrecovery of the recovered unreacted ethylene from the absorbent-ethyleneconjugant occurs via a pressure reduction from a pressure of theabsorption reactor to a pressure in a range of from about 0 psig toabout 10 psig, wherein recovery of the recovered unreacted ethylene fromthe absorbent-ethylene conjugant occurs at a temperature in a range ofabout 110° F. to about 200° F., and wherein the absorption solventsystem comprises copper chloride, aniline, and N-methylpyrrolidone.